IMAGE EVALUATiON TEST TARGET (MT-3) ^/ .<-'*%' M?< )?- 1.0 U.-z^ I.I ^l« IIIIM f~ iM III 2.2 .. 1^ mil 2.0 .8 1.25 1.4 1.6 1 ^ 6" — ► <^ //, ^l :¥ ^1 'm 7 % Photographic Sciences Corporation 23 WEST MAIN STREET WEBSTER, rJY 14550 (716) 872-4503 iV iV ^ 0- \ w.. - ril amlJul;/^ 1872. Utontrcal : PRINTED BY MITCHELL A WILSON. I / HISTORY OF THE NAMES CAMBRIAN AND SILURIAN IN GEOLOGY. Bv T. Sterhy Hunt, LL.D , F.R S. It is proposed in tlic following pages to give a concise account of the progress of investigation of the lower paleozoic rocks during the last forty years. The subject may naturally be divided into three parts: 1. The history of Silurian and Upper Cam- brian in Great Britain from 1831 to 1854 ; 2. Tiiat of the still more ancient paleozoic rocks in Scandinavia, Bohemia, and Great Britain up to the pnscnttimo, including the recognition by Bar- rande of the so-called primordial paleozoic fauna ; 3. The histoiy of the lower paleozoic rocks of North America. I. Silurian and Upper Cambrian in Great Britain. Less than forty years since, the various uncrystallinc sedimen- tary rocks beneath the coal-iorniation in Great Britain and in continental Europe were clas-sed together under the common name of grnyw,.ckc or grauw.-icke. a term adopted by geologists from Geinian miners, and originally applied to sandstones and other coarse sedimentary deposits, but extended so ;.s to include associated argillites and limestones. Some progress had been made in the study of this great Gr::yw;.cke formation, as it was called, and organic remains ju.d been described frem various parts of it ; but to two British geologists w.is reserved the honor of bringing order out of this hitherto confused f:roup of str;.ta, and establishing on stratigraphical and palconlological grounds a eucccssion and a gcologidl nomenclature. The work of these two investigators was begun independently and simultaneously in different parts of Great Britain. In 1831 and 1832. Sedgwick made a careful section of the rocks of North Wales from the Mcnai Strait across the ratige of Snowdon to the Berwyn hills, thus traversing in a south-eastern direction Caernarvon, Denbigh and Merionethshire. Already, he tells us, he had in IScil, made out the relations of the Bangor group, (including the Llan- berris slates and the overlying HarKch grits.) and showed that the fossiliferous strata of Snowdon occupy a .synclinal, and are jO^^I^^ stratigraphically several thousand feet above the horizon of the 'h ^-nyi^tL^Pi-ot^ 2 latter. Following up this investigation in 1S32, he ostablithcd the great Merioneth anticlinal, which brings up the lower rocks on the south-enst pide of Snowdon, and is the key to the struc- ture of North Walea. From those, as a base, he constructed a section jilong the line already indicated, over Great Arcnig to the Bala limestone, the whole forming an ascending scries of enorm- ous thickness. This limestone in the Bcrwyn hills is overlaid by many thousand feet of strata as we proceed eastward along the line of section, until at length the ea.*t( i dip of the strata is exchanged for a westward one, thus giving to the Berwyn chr.in, like that of Snowdon, a synclinal structure. As a consequence of this, the limestone of B:;la re-appears on the eastern side of the Berwyns, underlaid as before by a descending series of slates and porphyries. These results, with sections, were brought before the British Association for the Advancement of Science at its meeting at Oxford, in 1832, but only a brief and imperfect ae count of the communication of Sedgwick on this occ:;sion appears in the Proceedings of the Association. He did not at this time give any distinctive name to the series of rocks in question. [L E. & D. Philos. Mag. [1854] IV, viii, 495.] Meanwhile, in the same year, 1831, Muichison began the cx:imination of the rocks on the river Wye, along the southern border of Radnorshire. In the next four years he extended his researches through this and the adjoining counties of Hereford and Salop, distinguishing in this region four separate geological formations, each characterized by peculiar fossils. These forma- tions were moreover traced by him to the south-westward across the counties of Brecon and Caermarthcn ; thus forming a belt of fossiliferous rocks stretching from near Shrewsbury to the mouth of the river Towey, a distance of about 100 miles along the north-west border of the great Old lied sandstone formation, as it was then called, of the west of England. The results of his labors amonc; the rocks of this rea,ion for the first three years were set forth by Murchison in two papers pre- sented by him to the Geological Society of London in January, 1834. [Proc. Geol. Soc. II., 11.] The formations were then named as follows in descending order : 1. Ludlow, 2. Wcnlock, constituting together an upper group ; 3. Caradoc, 4. Llandcilo (or Builth) forming a lower group. Tiie Llandcilo formation, according to him, was underlaid by what he called the Longmynd and Gwastaden rocks. The non-fossiliferous strata of the Long- di 3 mynd hills in Shropshire were described as rising up to the cast from beneath the Llandcilo rocks; nnd asnppearinp: ngnin in South Wales, at the same gcrtlojrical horizon, at Gwastaden in Brecon- shire, nnd to the west of Llandovery in Caermarthenshirc ; con- stituting an underlying series of contorted slaty rocks many thous.ind feet in thickness, and destitute of organic remains. The position of those rocks in South Wales was, however, to the north-west, while the strata of the Longmynd, as we have seen, appear to the east of the fossiliferous formations. In the Philosopldcil Magazine for July, 1835, Murchison gave to the four formations above named the designation of Silurian, in allusion, as is well known, to the ancient British tribe of the Silurcs. It now became desirable to find a suitable name for the great inferior series, which, according to Murchipon, rose from beneath his lowest Silurian formations to the north- west, and appeared to be widely spread in Wales. Knowing that Sedgwick had long been engaged in the study of these rocks, ^lurchison, as he tells us, urged him to give them a British geo- graphical name. Sedgwick accordingly proposed for this great series; ci Welsh rocks, the appropriate designation of Cambrian, which was at once adopted by Murchisou for the strata supposed by him to underlie his Silurian system. [Murehison, Aniiiv. Address, 1842; Proc. Gcol. Soe. III., 641.] This was almost simultaneous with the giving of the name of Silurian, for in August, 1835, Sedgwick and Murehison made communications to the British Association at Dublin on Cambrian and Silurian Rocks. These, in the volume of Proceedings (pp. 59, GO) appear as a joint paper, though from the text they would seem to have been separate. Sedgwick then described the Cambrian rocks of North Wales as including three divisions: 1. The Upper Cam- brian which occupies the greater part of the chain of the Bcrwyns, where, according to him, it was connected with the Llandeilo formation of the Silurian. To the next lower division, Sedgwick gave the name of jMiddle Cambrian, making up all the higher mountains of Caernarvon and Merionethshire, and including the roofing-slates and flagstones of this region. This middle group, according to him, afforded a few organic remains, as at the top of Snowdon. The inferior division, designated as Lower Cam- bri in, included the crystalline rocks of the south-west coast of Caernarvon and a considerable portion of Anglesea, and con- sisted of chloritic and micaceous schists, with slaty quartzitcs and etito^Mt i^Jif . oMjUi slJj^ fubordinntc beds of terpentine and granular limestone ; the whole without organic rem lins. These ciystalline rocks were, however, soon Jiftcrwardts excluded by him fioni the Cambrian scries, for in iSiJS [Proc. Geo). Soc. II, GT!)] Sedgwick describes further the section from the 3Ieiiai Strait to the Berwyns, and assijrns to the ehloritic and micaceous schists of An-ilesea and Caernarvon a position iiil'eiior to the Canibrian, wliich he divides into two parts; viz.. Lower Cambrian, compreliendinjj the old slate series, up to the Bala limestone beds ; and Upper Cambrian, including the B.ila beds and the strata above them in the Berwyn chain, to which he gave the name of the Bala group. The dividing line between the two portions was subsequently extended downwards by Sedgwick to the summit of the Arenig slates and porphyries. The lower division was afterwards subdivide 1 by liim into the Bangor group, (to which the name of Lower Cambrian was henceforth to be restricted,! including the Llanbeiris roofing-sl ites and the JIarkxh grits or Barmouth smdstones; and the Festiiiiog group, which included the Lingula-fl igs and the succeeding Tremadoc slates. In the communication of Murchison to the same Dublin meet- ing, in August, 1835, he repeated the description of the four formations to which he had just given the name of Silurian; which were, in descending order, Ludlow and Wenlock (Upj)cr Silurian), and Caradoc and Llandeilo (Lower Silurian). The latter formation was then declared by Murehi?on to constitute the base of the Silurian system, and to offer in many places in South Wales distinct passages to the underlying slaty rocks, which were, according to him, the Upper Canibrian of Sedgwick. Meanwhile, to go back to 1834, we find that after Murchison had, in his communication to the Geological Society, defined the relation of his Llandeilo formation to the underlying slaty series, but before the names of Silui ian and Cambrian had been given to these respectively, Sedgwick and Murchison visited together the principal sections of these rocks from Caerraarthcnshire to Den- bighshire, The greater part of this region was then unknown to Sedgwick, but had been already studied by INIurehison, who in- terpreted the sections to his companion in conformity with the scheme already given ; according to which the beds of the Llan- deilo were underlaid by the slaty rocks vhich appear along their north-western border. When, however, they entered the region ■ which had already been examined by Sedgwick, and reached the section 00 the east side of the Bcrwyn?, the fossilifcrous beds of Meifod were nt once pronounced by Murcliison to be typical Ciir.idoc, while others in the vicinity were regarded asLlandeilo. The beds of Meifod had, on pnlcontological grounds, been by Sedgwick identified with thot^e of Glyn Ceirog, which are seen to be ininicdi ttely overlaid by Wenlock rocks. Those determina- tions of 31 urchison were, as Sedgwick tells us, accepted by him with great reluctance, inasmuch as they involved the upper part of his C.imbrian section in most perplexing difficulties. When however, they crossed together the Berwyn ch;.in to Bala, the limestones in this loclity were found to contain fossils nearly agreeing with those of the so-called Caradoc of Meifod. The examination of the section here presented showed, however, that those limestones are overlaid by a series of several thousand feet of strata bearing no resemblance either in fossils or in physical characters to the Weiilock formation which overlies the Caradoc beds of Glyn Ceirog, This series was, thereibre, by Murcliison supposed to be identical with the rocks which, in South Wales, he had placed beneath the IJandoilo, and he expressly deelarod that the Bala group could not be brought within the limits of his Silurian system. It may here be added . that in 1842 Sedgwick re-examined this region, accompanied by that skilled paleontologist, Salter, confirming the accuracy of his former sections, and showing moreover by the evidence of fossils that the beds of Meifod, Glyn Ceirog and Bala are very nearly on one parallel. Yet, with the evidence of the fos>ils beibrc him, Murehii^oii, in 1834, placed the first two in his Silurian system, and the last deep down in the Upper Cambrian ; and consequently was aware that on paleontological grounds it was impossible to separate the lower portion of his Silurian system from the Upper Cambrian of Sedgwick. (These names are here used for con- venience, although we arc speaking of a time when they had not been applied to designate the rocks in question.) Tliis fact was repeatedly insisted upon by Sedgwick, who, in the Syllabus of his Cambridge lectures, published very early in 1837, enumerated the principal genera and species of Upper Cambrian fossils, many of which were by him declared to be the same with those of the Lower Silurian rocks of Murcliison. Again, in enumerating in the same Syllabus the characteristic species of the Bala limestone, it is added by Sedgwick : " all of which arc com- ■ mou to the Lower Silurian system." This was again insisted 6 upon by him in 1838 find 1841, [Proc. Gcol. Soc. II. 679 ; III, 548.] It w.is not until 1840 that Bowman nnnnunccd the same conchision, which was reiterated by Sharpe in 1842. [Ilam- Bay, Mem. Geol. Sur. Ill, pa'-t 2, page G.] In 1839, Murehison published his SHun'mi Si/strin, dedicated to Sedgwick, a magnificent work in two volumes quarto, with a separate map, numerous sections and figures of fossils. The succession of the Silurian rocks, s there given, was precisely that already set forth by the author .n 1834, and again in 1S35; being, in descending order, Ludlow and Wenlock, constituting the Upper Silurian, and Caradoc and Llandcilo (including the Lower Llandeilo beds or Stiper-stones), the Lower Silurian. These arc underlaid by the Cambrian rocks, into which the Llan- deilo was said to oflFer a transition marked by beds of passage. Murehison, in f.ict, declared that it was impossible to draw any line of separation either lithological, zoological or stratigrapliieal between the base of the Silurian beds (Llandeilo) and the upper portion of the Cambrian, — the whole forming, according to him, in C lermarthcnshire, one continuons and conformable series from the Cambrian to the Ludlow. [Silurian System, pages 256, 358.] By Cambrian in this connection wc are to understand only the Upper Cambrian or Bala group of Sedgwick, as appears from tha express statement of Murehison, who alludes to the Cambrian of Sedgwick as including all the older slaty rocks of Wales, and as divided into three groups, but proceeds to say that in his present work (the Silurian System) he shall notice only the highest of these three. Since January, 1834, when Murchif-on first announced the stratigraphical relations of the lower division of what he after- wards called the Silurian system, the aspect of the case had materially changed. This divioion was no longer underlaid, both to the east in Shropshire and to the west in Wales, by a great unfossiliferous series. His observations in the vicinity of the Berwyn hills with Sedgwick in 1834, and the subsequently pub- lished statements of the latter had shown, that this supposed older series was not without fossils; but on the contrary, in North Wales, at least, held a fauna identical with that characterising the Lower Silurian. Hence the assertion of Murehison in his S!luri(tn Si/stcm, in 1839, that it was not possible to dvaw any line of demarcation between them. The position was very em- barrassing to the author of the iSilurian S^ntem, and for the mo- 7 mcnt. not less so to the discoverer of the Upper Cambrian scries. Mcanwliilc, the latter, as we have seen, in 1842 rc-cxauiincd with Salter his Upper Cambrian sections in North Wales, and satisfied himself of the correctness, both structurally and palcon- tologically, of his former determinations. Murchison, in his an- niversary address as President of the Geological Society in 1842, after rccountinp:, as wo have already done, the history of the naming by Sedgwick in 1835, of the Cambrian series, which Murchison supposed to underlie his Silurian system, proceeded as follows : " Nothing precise was then known of the organic con- tents of this lower or Cambrian system except that some of the fossils contained in its upper members in certain prominent lo- calities were published Lower Silurian species. Meanwhile, by adopting the word Cambrian, my friend and myself were certain that whatever njight prove to be its zoulogic il distinctions, this great system of slaty rocks being evidently inferior to those zones which had been worked out as Silurian types, no ambiguity could hereafter arise. * * =i< In regard, however, to a descending zoological order it still remained to be proved whether there was any type of ibs&ils in the mass of the Cambrian rocks different from those of the Lower Silurian series. If the appeal to na- ture should bo answered in the negative, then it was clear that the Lower Silurian type must be considered the true base of what I had named the protozoic rocks; but if characteristic new forms were discovered, then would the Cambrian rocks, whose place was so well established in the descending series, have al>.o their own fauna, and the paleozoic base would necessarily be re- moved to a lower horizon." If the first of these alternatives should be established, or in other words, if the fauna of the Cambrian rocks was found to be identical with that of the Lower Silurian, then, in the author's language, " the terra Cambrian must cease to be used in zoological classification, it being, in that sense, synonymous with Lower Silurian." That such was the result of palcontological inquiry, Murchison proceeded to show by repealing the announcements already made by Sedgwick in 1837 and 183'', that the collections made by the latter from the great scries of fossiliferous strata in the Berwyns, from Bala, from Snowdon and other Cambrian tracts, were identical with the Lower Silurian forms. These strata, it was said, contain throughout "the same forms of Orthis which typify the Lower Silurian rocks." It was farther declared by Murchison in this ■miiiaHHi 8 address, that researches in Germany, Belgium and Russia led to the conclusion that the " fossiliferous strata characterized by Lower Silurian Orthidau arc the oldest beds in which organic life has been detected." [Proc. Geol. Soc. Ill, 641, ct seq.] The Orthids here referred to arc, according to Salter, Orthls calligrammn, Dalm, and its varieties. [Mem. Gool. Survey III, part 2. 335- 337.] Meanwhile Sedgwick's views and position began to be misre- presented. In 1842, Mr. Sharpc, after calling attention to the fact that the fossils of the Bala limestone were, as Sedgwick had long before shown, identical with those of Murcliison's Lower Silurian, declared that Sedgwick had pliccd the Upper Cambrian, in whicli the Bala beds were included, beneath the Silurian, and that this determination had been adopted by Murchison on Sedg- wick's authority. [Proc. Geol. Soc. IV, 10.] This statement Murchison suffered to pass uncorrected in a complimentary re- view of Sharpe's paper in his next annual address (1843). In his iSiliiria, l.>it edition, page 25, (1854) lie speaks of the term Cambrian r.s applied (in 1835) by Sedgwick and himself "to a vast succession of fossHifcnmn strata containing undescribed fossils, tlie whole of which were supposed to rise up from beneath well-known Silurian rocks. The Govonimtnt geologists have shown thatthis.sH;yjosrlag. IV, viii, 488.] The section to the south-cast, commencing from the Llandeilo flags on the anticlinal, was made by Murehison the Silurian system, while the great mass of strata on the north-west side of the Llandeilo, (which is the complete representative of the Caradoc or Bila beds, partially concealed on the .south-west side.) was supposed by him to lie beneath the Llandeilo, and was called Cambrian ; (the Upper Cambrian of Sedgwick). These rocks, with the Llandeilo at their base, were in fact identical with the Bala group studied by the latter in North Wales, and arc now clearly traced through all the inter- mediate distance. This is admitted by Murehison, who sajs; " The first rectification of this erroneous view was made in 1842 by Prof. Ramsay, who observed that instead of being succeeded by lower rocks to the north and west, the Llandeilo flags folded over in those directions, and passed under superior strata, charged with fossils which Mr. Salter recognized as well-known types of the Caradoc or Bala beds." [Siluria, 4th cd., p. 57, foot-note.] The true order of succcssioo in South Wales was iu fact : 1, 12 Ll.indello ; 2, Cambrian (= Caradoc or Bala) ; 3, Wenlock and Ludlow ; 4, Old Red sandstone ; the C.iradoc or B da beds being repeated on the two sides of the anticlinal, but in great pirt concealed on the south-east side by the overlapping May Hill or Upper Llandovery rocks. Thcf^e latter, as has been shown, form the true bise of the upper «erics which, in the Silurian sections, was represented by the Wenlock and Ludlow, Murchi- son had, by a strange oversight, completely inverted the order of his lower scries, and turned the inferior members upside down. In fact, the Llandeilo flags, instead of being, as he had main- tained, superior to the Cambrian iCaradoc or B.ila) beds, wore really inferior to them, and were only made Silurian by a great mistake. The Caradoc, under different names, was thus made to do duty at two horizons in the Silurian system, both below and above the Llandeilo flags. Nor was this all, for by another error, as wc have seen, the Caradoc in the latter position was made to include the Pentamerus beds of the unconformably overlying series. Thus it clearly appears that with the exception of the relations of the Wenlock and Ludlow beds to each other and to the overlying Old Red sandstone, which were correctly de^er mined, the Silurian system of Murchison was altogether incorrect, and was moreover based upon a series of stratigraphical mistakes, which are scarcely paralleled in the history of geological investi- gation. It was thus that the Lower Silurian was imposed on the scien- tific world ; and we may well ask with Sedgwick, whether geologists " would have accepted the Lower Silurian classification and nomenclature had they known that the physical or sectional evidence upon which it was based had been, from the first, po- sitively misunderstood." Feeling that his own sections were, as has since been fully est iblished, free from error, Sedgwick na- turally thought his name of Upper Cambrian should prevail for the great B ila group. Hence the long and embittered discussion that i'ollowed, in which Murchison, in many respects, occupied a position of vantage as against the Cambridge professor, and finally saw his name of Lower Silurian supplant almost entirely that of Ujipcr Cambrian given by Sedgwick, who had first rightly defined and interpreted the geological relations of the group. In a paper read before the Geological Society in June, 1843, [Pioc. Gcdl Soc. IV, 212-223] when the perplexity in which the relations of the Upper Cambriau and Lower Silurian rocks were \ Wenlock and 3r Bik beds but ill great ing May Hill been shown, the Silurian w. Murchi- tho order of ipside down. 2 had main- beds, were by a great bus made to I below and lother error, as made to Y overlj'ing tion of the ther and to cctly deter r incorrect, il mi.stukes, cal iuvesti- 1 the scien- c, whether assification r sectional e first. po- is were, as gwick na- )revail for discusbion , occupied cssor, and t entirely •St lightly roup. no, 1843, vhich the jcks were 13 involved had not been cleared up by the discovery of Murcluson's errors in stratigraphy, Sedgwick proposed a compromise, accord- ing to which the strata from the Bala limestone to the ba?e of the Wenlock were to take the name of Cambro-Silurian ; while that of Silurian should be reserved for the Wenlock and Ludlow beds, and for those below the Bala the name of Cambrian should be retained. The Festiniog group (including what were subse- quently named the Lingula-flags and the Trcmadoc t^latcs) would thus be Upper instead of Middle Cambrian, the original Upper Cambrian being henceforth Cambro-Silurian ; it being understood that, wherever the dividing line might be drawn, all the groups above it should be called Cambro-Silurian, and all those below it Cambrian. This compromise was rejected by IMurchison, who in the map accompanying the first edition of his Silurin, in 1854, extended the Lower Silurian color so as to include all but the lowest division of tlie Cambrian; viz., the Bangor group. When, however, the relations of Upper Cambrian and Silurian were made known by the di.scoveries of Sedgwick and the Government surveyors, this compromise was seen to be uncalled for, and was withdrawn in 1854 by Sedgwick, who re-claimed the name of Upper Cambrian for his Bala group. In June, 1843, Sedgwick proposed that the whole of the fos- siliferous rocks below tlie horizon of the Wenlock should be designated Protozoic, and on the 2nth of November, 1843. pre- sented to the Geological Society an elaborate paper on the Older Paleozoic (Protozoic) Rocks of North Wales, with a colored geological map. This paper, which embodied the results of the researches of Sedgwick and Salter, was not, however published at length, but an abstract of it was prepared by Mr. Warburton, then president of the society, with a reduced copy of the map. (Proc. Geol. Soc. IV. 212 and 251-2G8 ; also Geol. Jour. I, 5-22.] In this map of Sedgwick's three divisions were established, viz., the liypozoic crystalline scliists of Caernarvonshire, the " Fruio- zoi'c," and the " Sihtrian.'' On the legend of the reduced map, as published by the Geological Society, these latter names were altered so as read ^^ Lower Silurian (Frotozoicf^ and " Uj>pn' SilurianJ^ These changes, in conformity with the nomenclature of Murchison, were, it is unnecessary to say, m ide without tlie knowledge of Sedgwick, who did not inspect the reduced and altered map until it was appealed to as an evidence that lie had abandoned his former ground, and had recognized the equivalency Mi u 1 1 of the whole of his Cambrian with the Lower Silurian of Mur- chison. The reader will sympathize with the indignation with which Sedgwick declares that his map was " most unwarrantably tampered with," and will, moreover, learn with surprise, that an inspection of the proof-sheets of Warburton's abstract of Sedgwick's paper was refused him, notwithstanding his repeated solicitations. The story of all thin, and finally of the refusal to print in the pages of the Geological Journal the reclamations of the venerable and aggrieved author, make altogether a painful chapter, which will be found in the Philos. Magazine, for 185-i [IV, viii, pp. 301-317, 359-370, and 483-50G] and more fully in the Synopsis of British Paleozoic Rocks, which forms the introduction to McCoy's British Paleozoic Fossils. In connection with this history it may be mentioned that in March, 1845, Sedgwick presented to the Geological Society a paper on the Comparative Classification of the Fossiliferous Hocks of North Wales and those of Cumberland, Westmoreland, and Lancashire ; which appears also in abstract in the same volume of the Geological Journal that contains the abstract of the essay and the map just referred to. [I, 442.] That this ab- stract also is made by another than the author is evident from such an expression as " the author's opinion seems to be grounded on the following facts, etc.," (p. 448) and from the manner in which the terms Lower and Upper Silurian are applied to certain fossiliferous rocks in Cumberland. Yet the words of this ab- stract are quoted with emphasis in Siluria [1st cd., 147] as if they were Sedgwick's own language recognizing Murchison's Silurian nomenclature. II. — Middle and Lowek Ca.mijrian. Investigations in continental Europe were, meanwhile, prepar ing the way for a new chapter in the history of the lower paleozoic rocks. A series of sedimentary beds in Sweden and Norway had long been known to abound in singular petrifications, some of which had been examined by Linnaeus, who gave to them the name of EntomoIitJii. They were also studied and described by Wahlenberg and by Brongniart, the latter of whom, from two varieties of the IJutomolithns paradoxus, Linn, established in 1822 two genera, ParaJoxUhs and Agiiostus. In 182G ap- peared a memoir by Dalman on the Palseadoc or so-called Trilo- 15 irian of Jlur- ignation with nvvarrantably surprise, that i abstract of his repeated he refusal to ?iamations of cr a painful le, for ]854 more fully 1 forms tlio •nod that in 1 Society a ?ossiliferous vstmorcland, n the same tract of the lat this ab- ident from >o grounded manner iri 1 to certain of this ab- 147] as if furchison's le, prepar r paleozoic orway had , sonic of them the icribcd by from two jlishcd in 182G ap- ed Trilo^ bites; which was followed, in 1828, by his classic work on the same subject. [Uber de Palaciden oder so-gcnantcn Trilobitcn, 4to. with six plates, Leipsic] In these works were doscribod and figured, among niiny others, two genera — O/e/'ws, which included Puradoxlths, Brongn. and B'lfttis, including Agnostiis of the same author. Meanwhile, Hisinger was circfully studying tho strata in which these trilobites were found in Gothland, and in the same 3'ear (1828) publi^^hod in his Anteckniugnr, or Notes i on the Physical and Geognostical Structure of Norway and Sweden, a colored geologic d map and section of these rocks as they occur in the county of Sk iraborg; where three sm ill cir- , cumscribjd arcis of neirly horizont.il fossiliferous strata are J shown to rest upon a floor of old crystalline rocks, in .come parts granitic and in others gneissio in character. The section and map, as given by Hisinger, show the succession in (he princip d area to be as follows, in ascending order : 1. granite or gneiss ; 2. sandstone; 3. alum-slates; 5. orthoccratitc-linicstones ; 4. clay- slates. By a curious oversight the colors on the legend arc wrongly arranged and wrongly numbered, as above ; for in tho map and section it is made clear that the suocossion is that just given, and that the clay-slates (4), instead of being bjlow, are above the orthoccratite-limestoncs (5). In 1837, Hisinger published his great work on the organic remains of Sweden, entitled Lethoc'i Suecica [4to. with forty-two plates.] In this he gives a tabular view, in descending order, of the rock-formations, and of the various genera and species de- scribed. The rocks of the areas just noticed appear in his fourth or lowest division, under the head of Furmailones tmnsitiunis, and arc divided as follows : a. Strata calcarea recentiora Gottlandios. 6. Strata scliisti argillacci, c. Strata schis-ti aluminarls. (i. Strata calcarea antiquiora. e. Strata saxi arcnacci. The succession thus given was however erroneous, and pro- bably, like the mistake in the legend of the same author's map just mentioned, the result of inadvertence, the true position of the alum-slates (c) being between tho older limestone (d) and the basal sandstone (c). This is shewn both by Ilisinger's map of 1828, and by tho testimony of subsequent observers. In Murchisou's work on the Geology of Kussiu in Europe, publish- ! HI 16 cd in 1845, thoro ia given (page 15 et seq.) nn account of his visit to tliis region in company with Prof. Loven, of Christiania ; which, with figures of the sections, is reproduced in the different editions of Siluria. The hill of Kinnckulle on Lake Wcner, is one of the three areas of transition rocks delineated on tlic map of Ilisingcr above referred to. Ecsting upon a fl it region of nearly vertical gneissic .strata, we have, according to Murchi.«on : 1. a fucoidal sandstone; 2. alum-slates; 3. red orthoceratite limestone; 4. black graptolitic slates; the whole series being little over 1000 feet in thickness, and capped by erupted green- Btono. Above these higher slates there are found in some parts of Gothland, other limestones with orthoccratitcs, trilobites and corals, the newer limestone strata («) of Ilisingcr ; the whole over- laid by thin sandstone beds. These higher limestones and sand- stones contain the fauna of the Wenlock and Ludlow of Eng- land ; while the lower limestones and graptolitic slates afford Cah/mc7ie BhnncnhnchU, Orthls caUigrcnnma, and many other species common to the Bala group of North Wales. The alum- slates bolow these however, contained, according to Ili^inger, none of the .species then known in British rocks, but in their stead five species of Olcinis and two o? Baft its (Agnosfuti.) In 1854, Angelin published his Pahtontolog lea Scandiuavica, part I, Cnistncea formationis transitlonis, [4to. forty-one plates] in which he divided the scries of transition rocks above described by Hisinger into eight parts designated by Roman numerals, counting from the base. Of these I was named Rrgio Fnroidarnm, no organic remains other than fucoids being know therein ; wiiile the remaining seven were named from their characteristic genera of trilobites, which were as follows, in ascending order ; certain letters being also used to designate the parts: IL (A) Olenus; in. (B) Conocoryphc ; YV . (BC) Ceratopyge; V. (C) Asaphus ; VI. (D) Trinucieus; VII. (DE) llarpes; VIII. (E) Cryp- tonymus. In the Rcrjlo Olcnonnn (II) was found also the allied f^cnus Paradox Uh's, With regard to the characteristic genus of Regio III., the name of Co)iocori/phc was proposed for it by Corda in 1847, as synonymous with Ttcnkcr snmncoi' Co nocrjdut- lus (Couocephah'(cs) already appropriated to a genus of insects. Meanwhile, the similar crustaceans which abound in the tran- sition rocks of Bohemia had been studied and described by Hawle, Corda and Beyrich, when Barrande began his admirable investigations of this ancient fauna and of its stratigraphical re- 17 account of his of Cliristiania ; in tlie difForcnt Lake Wcncr, is 2(1 oil the map flit region of to Murchison : S ortiiocerMtite e series bcinc erupted grceii- in sonic parts trilobites and he whole over- 3ncs and sand- d]ow of En2- ! iihitcs afford 1 many other . The alum- to Ilisinger, but in their losfun.) '('(nulliiavica, y-ono plates] ove described an nunicrab, Fiiroidanim, icrciii; while ristic genera dor; certain (A) Olenus; ) As.iphus ; (E) Cryp- so the allied tic genus of I ibr it by Conocrplia- of insects. II the tran- scribed by s admirable ;i[ihical re- lations. He soon found that beneath the horizon characterized by fossils of the Bala group (Llandcilo and Caradoc) there ex- isted in Bohemia a series of strata distinguished by a remaikablc fauna, entirely distinct from anything known in Great Britain, but closely allied to that of the ahini-slates of Scandinavia, cor- responding to Begiones II. and III. of Angclin. To this he gave the name of the first or priniordi.il fauna, and to the rocks yielding it that of the Primordial Zone. Besting upon the old gneisses of Bohemia appears a series of crystalline schists design- ated by Barrande as Etage A, overlaid by a series of sandstones and conglomerates, Etayc B, upon which repose the fossiliferous argillitcs of the primordial zone or Et(( > desiijn.-ition of ic of St. David's 2, Salter found black shales at ly on the green :'ch beds. Tiie ;ks, and it was otii jicrc and in i groat mass of laractcrizcd by levian beds are ^cst portion of 'lit conforniity, i the bottom ; represented li Wales, near e sandstones, valeiit of the nfossiliferous discovery in 1 Linuulella, Hir. XXIII, cximinition ill the dis- 1 typo, and c Moiievian ; fossilifcmus :^eindinavi:i, « was m ido •thcr details ^Uy, 1871, by ^rcssr.*?. Ilarkncss and Hicks, whoso pnpcr on the Ancient Hocks of St. D.ivid's Promontory appears in the Gcolo<,ncal Journal for November, 1871. [XXV^III, 384.] The Cam- brian sediments hero rest upon an older .series of crystalline stra- tified rocks, described by the gef»lo.:ic.il surveyors as syenite and grecnstonj, and hivin;x a north-west strike. Lyiii,:: unconforra ibly upon these, and with a north-c.ist strike, we h ivc the f*)llowing series, in ascondinp^ order: l.quirtzo^c conjjlomMMtc, GO feet; 2. greenish fl iggy sandstones, 4G0 foot ; 3. rod fl igs or .slaty beds, 50 feet, containing Llitgnhihi fvi'rmj'nivit, besides a larger species, Bisciiut, and Lrprrditi'i Cambrciisis ; 4. puri)le and greenish sandstones, 1000 foet ; 5. yellowish gray sindstones, fl igs and sliales, 150 foot, with Plutoiiin, Conucori/phc, Micr'nh'scus, Aguosttis, Theca and Prolospoiir/iit ; G. gray, purple and red flaggy sandstones, with most of the above genera, 1500 feet; 7. gray fl iggy beds, 150 foot, with Par idoxlihs; 8. true Mcnevian beds, richly fbssiliforous, 500 feet. Tlie 1 itter are the prob.blc equivalent of the base of Barrando's Etagc C, and at St. D ivid's are conformably overlaid by the Lingul.i-fligs; bc'neath which wo have, including the Menevi m, a conformable series of 3370 foot of uncrystallinc sedimonts, fossiliforous neirly to the b iso, and liolding a well-marked fauna distinct from anything hitherto known in Great Britain or elsewhere. The Jlenevian beds are connected with the underlying strata by the presence of LiiigulvJli fcrnigiucn, Dlscina piknlus, and Oboh'lla sagittati's, which extend througli the whole series ; and also by the genus Paradoxides, four species of which occur in these lower strata; from which the genus Clonus, which charac- terizes the Lingula-fl Igs. seems to be absent. To a large tubcr- culatcd trilobite of a new genus found in these lowest rocks the name o? Phitonia SccJyw'tckll has boon given. Hicks has proposed to unite the Monevian with the Harlech beds, and to make the summit of the former the dividing line between the Lower and Middle Cambrian, a suggestion which has been adopted by Lyell. [Proc. Brit. Assoc, for 18G8, p. C8, and Lyell, Student's Manual of Geology, 4GG-4G9.] Both Phillips and Lyell give the name of Upper Cambrian to the Lingula-flags and the Trcmadoc slates, which together constitute the ]Middle Cambrian of Sedgwick, and concede the title of Lower Silurian to the Bala group or Upper Can'ibrian of Sedgwick. The same view is adopted by Liuuarssoa in 99 Sweden, who places tlic line between Cambrian and Silurian at the base of the Llandeilo or the second fauna. It was by following these authorities that I, inadvertently, in my address to the Amoricm Association for tlie Advancement of Science in Au,2;ust, 1871, jrave this liorizon as the original division between Cambrian and Silurian. The reader of the first part of this paper will see with how much justice Sedgwick claims for the Cambrian the whole of the fossiliferous rocks of Wales beneath the base of the May Hill sandstone, including both the first and the second fauna. I cannot but agree with the late Henry Darwin Rogers, who, in 185G, reserved the designation of " the true Euro- pe:m Silurian " for the rocks ahocc this horizon. [Keith Johnson's Physical Atlas, 2nd ed.] The Lingul;'-fl igs and Tremadoc slates have been made tlie subject of careful stratigraphical and paleontological studies by the Geological Survey, the results of which arc set forth by Ramsay and Salter in the third volume of the Memoirs of the Geologic il Survey, published in 18()6, and also, more concisely, in the Anniversary Address by the former to the Geological Society in 1803. [Geo). Jour. XIX, xviii.] The Lingula flags (with the underlying 3Ienevian, which resembles thcra lithologically) rest in apparent conformity upon the purple Harlech rocks both in Pembrok'-'shire and in Merionethshire, where the latter appear on the great Merioneth anticlinal, long since pointed out by Sedg- wick. The Lingula-fl:ig!(, (including the Menevian) have in this region, according to Ramsay, a thickness of about 6000 feet. Above thc^e, near Tremadoc and Fcstiniog, lie the Tremadoc slates, which are hero overlaid, in apparent conformity, by the Lower Llandeilo beds. At a distance of eleven miles to the north-west, however, the Tremadoc slates disappear, and the Lingula-fligs are represented by only 2,000 feet of strata ; while in parts of Caernarvonshire, and in Anglcsca, the whole of the Lingula-fligs and moreover the Lower Cambrian rocks, are wanting, and the Llandeilo beds rest directly upon the ancient crystalline schists. In Scotland and in Ireland, moreover, the Lingula flags, are wholly absent, and the Llandeilo rocks there repose unconforniably upon grits regarded as of Lower Cambrian age. Thus, without counting the Tremadoc slates, which are a local formation, unknown out of Merionethshire, we have (includ- ing the Bangnr group and Lingula-flags,) beneath the Llandeilo, ovt'v 9,000 ft'ct of fossiliferous strata, which disappear entirely in ' < > ' r 23 i 1 f -> the distance of a few riiles. From a careful survey of all the facts, the conclusion of Ranisny is irresistible, that there exists between the Lingula-fligs and the Llandeilo not luercly one, but two great stratigrapliical breaks in the succession ; the one between the Lingula-fl.igs and the Lower Treniadoc slates, and the other between the Upper Tn^madoc slates and the Lower Llandeilo. This conclusion is conGrmed by the fact that there exists at each of these horizons a nearly complete paleontological break. The fauna of the Tremadoc slates is, according to Salter, almost en- tirely distinct from that of the Lingula-flags, and not less distinct from that of the so-called Lower Llandeilo or Arenig rocks, (the equivalents of the Skiddaw slates of Cumberland). Hence, says llamsay, it is evident " that in these strata we have three per- fectly distinct zones of organic remains, and therefore, in com- mon terms, three distinct formations." The paleontological evidence is thus in complete accordance with that furnished by stratigraphy. We cannot leave this topic without citing the conclusion of Ramsay that " each of these two breaks necessarily implies a lost epoch, stratigraphieally quite unrepresented in our area ; the life of which is only feebly represented in some cases by the fossils common to the underlying and overlying forma- tion." Ill connection with this remark, which we conceive to embody a truth of wide application, it may be said that strati- graphical breaks and discordances in a geological series, may, d priori, be expected to occur most frequently in regions where this series is represented by a large thickness of strata. The ac- cumulation of such masses implies great movements of subsi- dence, which, in their nature, are limited, and are accompanied by elevations iu adj icent areas, from which miy result, over these areas, either interruptions in the process of sedimentation, or the removal, by sub-aerial or sub-marine denudation, of the sedia)ent8 already formed. The conditions of succession and distribution it miy be conceived, would be very different in a region where the period corresponding to this same geological series was marked by comparatively small accumulations of sediment upon an ocean- floor subjected to no great movements. This contrast is strikingly seen between the conformable series of less than 2,000 feet of strata which in Scandinavia are char- acterized by the first three paleozoic faunas (Cambrian and Si- lurian) and the repeatedly broken and dibcordaut successioa of 24 more tlmn 30,000 feet of sediments,-!^ which In Wales arc their piileontologicil equivalents. It must, however, be considered that in re,i>ions of sm ill accumuLition where, as in Scandinavia, the formations arc thin, there may be lost or unrepresented zoolo- gical epochs whoso place in the series is marked by no sti'uti- graphical break. In such comparatively stable regions, move- ments of the surface sufficient to cause the exclusion, or the dis- appearance by removal, of the small thickness of strata corrcs-" ponding to an epoch, may take place without any conspicuous marks of stratigraphical discordance.- The attempt to establish geological divisions or horizons upon stratigraphical or puleontological breaks must always prove falla- cious. From the nature of things, these, whetlier due to non-de position or to subsccpient removal of deposits, must be local; and we can say, confidently, that there exists no break in life or in sedi- mentation which is not somewhere filled up and represented by a continuous and conformable succession. While we may define one period as characterized by the presence of a certain fauna, which, in a succeeding epoch, is replaced by a different one, there will always be found, in some part of their geographical distribution, a region where the two fiunas commingle, and where the gradual disappearance of the old before the new may be studied. The division of our stratified rocks into systems is therefore unphi- losophical, if we assign any definite or precise boundaries or limi- tations to these. It was long since said by Sedgwick with regard to the whole succession of life through geologic time, — that all belongs to one great syatcma natiira: [Philos. Mag. IV. viii, 359 ] We have already noticed that Barrande, as early as 1852, gave the name of Primordial Silurian to the rocks which, in Bohemia, were marked by the first fauna ; although he, at the f * Tlu' Longm.vnd rocks in Sliropsliire aro alone estimated at 20,000 foct ; but thfii' supposcii (.quivalonts, tlie llarli'cli rocks of Pembroke* shire, have a nuaisi red thickness of 3,;500, while the Llnhberris and Ilaiiccii rociis together, in North V.'.dcs, equal from 4,000 to 7,000 fjct, and the Lingiihv-tlags anrl Treniadoc slates, united, about 7,000 fjet. 'Die Bahi f^Moup in tlie JJenvyns exceeds 12,000 feet, and tiio proper Silurian, fiom the base of the Upper Llandovery or May Hill sandstone, attains from 5,000 to G,000 feet: so that the aggregate of 30,000 feet may hj considered b.^low the truth. [Mem. Geol. Survey, III, part 2, pages 12, 222, and Siluria, 4lh cd. 18 J. J S5 same time, recognized this as distinct from and older fhaii the second f'aunn, discovered in thcLlandeilo rocks, which Murchison had dcchircd to represent the dawn of organic life. Into the reasons which led Barrande to include the rocks of the first, second and third fiunas in one Silurian system, (a view which was at once adopted by the British Geological Survey and by Murchison himself.) it is not our province to inquire, but we desire to call attention to the fact that tiic latter, by his own principles, was bound to reject such a classification. In his address before the Geological Society in 1S42, (already quoted in the first part of this piper,) he declared that the discussion as to the value of the term Cambrian involved the question '•whether tliero was any type of fossils in the mass of the Cambrian rocks different from those of the Lower Silurian series. If the appeal to nature should be answered in the negative, then it was clear that the Lower Silurian type must be considered the true base of what I had named the protozoic rocks ; but if characteristic new forms were discovered, then would the Cambrian rocks, whose place was so well established in the descending series, have also their own fauna, and the paleozoic base would necessarily be removed to a lower horizon." , In the event of no distinct fauna being found in the Cambrian series, it was declared that " the term Cambrian must cease to be used in zoological classification, it being, in that .'cnse, .synony- mous with Lower Silurian." [Proc. Geol. Soc. Ill, G41 et .«:cq.] That such had been the result of paleontological inquiry 3Iur- chison then proceeded to show. Inasmuch as the only portion of Sedgwick's Cambrian which was then known to be Ibssilifeious, was really above and not below the Llandtilo rocks, which Mur- chison had taken for the base of his Lower Silurian, his reason- ing with regard to the Cambrian nomenclature, based on a false datum, was itself fallacious ; and it might have been expected that when the government surveyors had shown his stratigrapliical error, Murchi.son would liave rendered justice to the nomenclature of Sedgwick. But when, still later, a farther " appeal to nature" led to the discovery of " characteristic new forms," and estab- lished the existence of a " type of fossils in the mass of the Cam- brian rocks, different from those of the Jiowcr Silurian series," Murchison was bound by his own principles to recognize the name of Cambrian for the great Festiniog group, with its primordial 3 26 fauna, even though Barrande and the government surveyors should unite in calling it Primordial Silurian. He however chose the opposite course, and now attempted to claim for the Silurian system the whole of the Middle Cumbrian or Fostiniog group of Sedgwick, including the Trcmadoc slates and the Lingula-fltigs. The grounds of this assumption, as set forth in the successive editions of Siluria from 1854 to 18G7, and in various memoirs, may be included under three heads: first that the Lingula-fl:igs have been found to exist in some parts of his original Silurian region ; second, that no clearly-defined base had been assigned by him to his so-called system ; and third, that there are no means of drawing a line of demarkation between these Middle Cambrian formations and the overlying Llandeilo. With regard to the first of these reasons, it is to be said that the only known representatives of the Lingula-flags in the region described by Murchison in his Silurian JSi/sfcm are the black slates of Malvern ; and some scanty outliers which, in Shropshire, lie between the old Longmynd rocks and the base of the Stiper- stones. The former were then (as has already been shown) sup- posed by him to belong to the Llandeilo, or rather to the passage- beds between the Llandeilo and Cambrian (Bala) ; while with regard to the latter, Ramsay expressly tells us that they were not originally classed with the Silurian, but have since been included in it. [Mem. Gcol. Sur. Ill, part 2, page 9 ; and 242, foot-note.] The Llandeilo beds were by Murchison distinctly stated to bo the base of the Silurian system [Sil. Sys. 222.] ; and it was far- ther declared by him that in Shropshire, (unlike Caermarthen- shire.) " there is no passage from the Cambrian to the Silurian strata," but a hiatus, marked by disturbances which excluded tho passagc-b'^'^s, and caused the Lower Silurian to rest unconform-* ably upon the Longmynd rocks. [Ibid, 25G ; and plates 31, sec- tions 8 and G; 32, section 4.] But in iSiliiria [1st. ed. 47] tho two are stated to be conformable; and in (he subsequent sections of thi.s region, made by Aveline, and published by the Geological Survey, the evidences of this want of conformity do not appear* Murchison at that time confounded the rocks of the Longmynd witli the Cambrian (Bala) beds of Cacrmarthcnshirc and Brecon. [Sil. Sys. 41G.] Hence it was that he gave the name of Cam- brian to the former; and this mistake, moreover, led him to placo the Cambrian of Cacrmarthenshire beneath the Llandeilo. It is clear that if he claimed no wcU-dciiued base to the Llaudcilo 27 rocks in this latter (their typical region), it was because he saw them passing into the overlying B;il:i beds. There was, in the error by wliich he placed below the Llandeilo, strata which were really (dnve them, no ground whatever for afterwards including in his Silurian system, as a downward continuation of the Llan- deilo rocks (which arc the basal portion of the Bala group), the whole Ft'.stiiiiog group of Sedgwick; whose infra-position to the Bala had been shown by the latter long before it was known to be fos!«iiiferous. It was however claimed by Murchison that no lino of separa- tion can be drawn between these two groups. The results of Ramsay and of Salter, as set forth in the address of the former before the Geological Society in 18G3, and more fully in the Memoirs of the Geological Survey [vol. III. part 2] published in ISGG, with a preface by himself, as the director of the Survey, arc completely ignored by Murchison. The reader familiar with these results, of which we have given a summary, finds with sur- prise that in the last edition of Sllttria, that of 1867, they are noticed in part, but only to be repudiated. In the five pages of text wliich arc there given to this great Middle Cambrian divi- sion, we are told that the distinction between the Lower Trema- doc and the Lingula-fl.igs " is difficult to bo drawn," and that the Upper Tremadoc slate passes into and forms the lower part of the Llandeilo, "into which it graduates conformably." (Siluria, 4th cd. p. 4G.) In each of these cases, on the contrary, according to Ramsay, there is observed "a break very nearly complete both in genera and species, and probible unconformity ;" the evidence of the paleontologie:il break being furnished by the careful studies of Salter; while that of the stratigraphical break, as wc have seen, leaves no reason for doubt. [Mem. Geol. Sur. Ill, part 2, pages 2, IGl, 234.] The student of tSihtria soon learns that in all cases where Murchison's pretensions were concerned, the book is only calculated to mislead. The reader of this history will now be able to understand why, notwithstanding the support given by Barrande, by the Geologi- cal Survey of Great Britain, and by most American geologists to the Silurian nomenclature of Murchison, it is rejected, so far as the Lingula-fljgs and the Tremadoc slates are concerned, by Lycll, Phillips, Davidson, Harkncss and Hicks in England, and by Linnarsson in Sweden. These authorities have, however, admitted the name of Lower Silurian for the Bala group or -^>p~ 28 Upper Cambrian of Sedgwick ; a concession which can hardly be defended, but which apparently found its way into use at a time when the yet unravelled perplexities of the Weli-h rocks led Sedgwick himself to propose, for a time, the name of Cambro- Silurian for the Bala group. This want of agreement among geologists as to the nomenclature of the lower paleozoic rocks, causes no little confusion to the learner. We have seen that Henry Darwin llogers followed Sedgwick in giving the name of C;imbri;in to the whole paleozoic scries up to the base of the May Hill sandstone; and the same view is adopted by Woodward in his Manu;il of the Mollusca. The student of this excellent book will find that in the tables giving the geological range of the mollusca, on pages 124, 125 and 127, the name, of Cambrian is used in Sid K cf rt" fi 5 !^ >- e c 5 *^ ^ O § • - ^ G - ? Ct "^ ^ r^ c5 P s •J ""• r3. o Ph o o p C 33 III. Cambrian and Silurian Rooks in North America. In accordance with our plan we now proceed to sketch the his- tory of the hmer paleozoic rocks in North America. While European f^eoloj:;ist,s were carrying out the researches which have been described in the first and second parts of this paper, Ame- rican investigators were not idle. The geological studies of Eaton led the way to a systematic survey of the state of New York, the results of which have been the basis of most of the subsequent geological work in eastern North America, and which was beo-un by legi.slative enactment in 1836. The state was divided fnto four districts, the work of examining and finally reporting upon which was committed to as many geologists. The first or south- eastern district was undertaken by Mather, the second or north- eastern by Emmons, the third or central by Vanuxcm, and the fourth or western by James Hall ; the paleontology of the whole being left to Conrad, and the mineralogy to Beck. After various annual reports the final results of the survey appeared in 1842. The whole .series of fo.ssiliferous rocks known, from the basal or Potsdam sandstone to the coal-formation, was then described as the New York system. At that time the published researches of British geolo"-ists furnished the means of comparison between the organic remains found in the rocks of New York, and those then known to exist in the paleozoic strata of Great Britain. Prof Hall was thus enabled in his (Jeology of the Fourth District of New York, to declare, from the study of its fossils, that the New York system included the Devonian of Phillips, the Silurian of Murchison, and the Cambrian of Sedgwick ; meaning by the latter the Upper Cambrian, or Bala group, which alone was then known to be fossi- liferous. Prom the evidence then before him, he concluded that the Upper Cambrian was represented in the New York system 34 m II! 1 1 IH-'i- by the whole of tlie rocks from the base of tlie TJtica shite, dowiiward, with tlit^ probiibh; exception of the Potsdam sand- 8ton(( ; while he conceived, partly on lithological grounds, that the IJtica and lliidson-River groups represented the .Llandcilo and Caradoc, or the Lower Silurian of Murchison [loc. cit. pages 20, 29, 31]. I'he origin u\ the ('and)rian and Silurian cr»n- troversy, and the errors by which the Llandcilo and a part of the Caradoc had by Murchison been classed as a series distinct fVom the Bala grouj», wen; not then known; but in a note to this report [page 20,] ILill informs us of the declaration of Murchison, already (juotcd from his address of 1842, that the Cambrian, so far as then known, could not. on palcontological grounds, be dis- tinguished from his Lo\v(!r Silurian. Enunons mcmwliile had exan)ined in eastern N(^w York ainJ western New England a series of fossiliferous rocks, which on lithological and stratigraphical grounds, he regarded as older than any in tht; New York system ; a view which had been previously maintained by Eatcm. Holding, with Hall, that the lower menibers of the New York system were tlie e(|uivalents of the Upper Cambrian of Sedgwick, he looked upon the fossiliferous rocks which he placed beneath them, as the representatives of the Lower Cambrian. By this name, as we have seen, Sedgwick, in 1838, designated all those uncrystalline rocks of North Wales which he subsequently divided into Lower and Middle Cam- brian, and which lie ))eneath the base of the Bala group. When Murchison, in 1842, iu his so often quoted declaration, a.sserted that " the term Cambrian must cease to be used in zoological classification, it being in that sense synonymous with Jjower Si- lurian," he was speaking only on palcontological grounds, and, disregarding the great Lower and Middle Cambrian divisions of Sedgwick, had reference only to the Upper Cambrian. This how- ever was overlooked by Emmons, who feeling satisfied that the sedimentary rocks which he had examined in eastern New York were distinct from those which he, with Hall, regarded as corres- ponding to the Bala group or Upper Cambrian, (the Lower Silurian of Murchison), and probably equivalent to the inferior portions of Sedgwick's Cambrian ; and supposing that the latter term was henceforth to be eflFaced from geology (as indeed was attempted shortly after, in the copy of Sedgwick's map published in 1844 by the Geological Society) devised for these rocks the name of the Taconic system, as synonymous with the Lower 35 (and Middle) Cambrian of Sedgwick. These conclusions were Bet forth by hiui in 1H42, in his report on the Geology of the Northern DiHtrictof New York [page H)2]. See also his Agricul- ture of New York [I, 49] the fifth chapter of which, " On the Taconic 8y«teni," was also publi.sh(!d separately in 1844 ; when the presence of distinctive organic remains in the rocks of this series was first announced. Meanwhile to Prof Hall, sifter the completion of the survey, had been conimittcid the task of studying and describing the organic remains of the state, and in 1847 appeared the first volume of his great work on the " Paleontology of New York." Since 1842 he had been enabled to examine more fully the or- ganic remains of the lower rocks of the New York system, and to compare them with those of the old world ; and in the Intro- duction to the volume just mentioned [page xix] he announced the in)portant conclusion that the New York system itself con- tained an older fauna than the Upper Cambrian of Sedgwick. According to Hall, the organic forms of the Calciferous and Chazy formations had not yet been found in Europe, and our compari- son with European fossiliferous rocks must commence with the Trenton group. He however excepted the Potsdam sandstone, which already, in 1842, he had conceived to be below the Upper Cambrian of Sedgwick, and now regarded as the probable equi- valent of the Obolus or Ungulite grit of St. Petersburg. Thus Emmons, in 1842, asserted, on lithological and stratigraphical grounds, the existence, beneath the base of the New York system, of a lower and unconformable series of rocks, in which, in 1844, he announced the discovery of a distinctive fauna. Hall, on his part, asserted in 1842, and more fully in 1847, that the New York system itself held an older fauna than that hitherto known in the British rocks. It is not necessary to recall in this place the details of the long and unfortunate Tacoiiic controversy, which I have recently dis- cussed in my address before the American Association for the Advancement of Science in August, 1871. It is however to be remarked that Hall, in common with all other American geolo- gists, followed Henry D. Rogers in opposing the views of Hiu- mons, whose Taconic systejn was supposed to represent either the whole or a part of the Champlain division of the New York system ; which included, as is well known, all of the fossiliferous rocks up to the base of the Oneida conglomerate (and also this 36 ' i: latter, according to Emmous) ; thus comprehending both the first and the second paleozoic fauna ; as shown in the table on page 312. Emmons, misled by stratigraphical and lithological considera- tions, complicated the question in a singular manner, which scarcely finds a parallel except in the history of Murchison's Silurian sections. Completely inverting, as I have elsewhere shown, the order of succession in his Taeonic system, estimated by him at 30,000 feet, he placed near the base of the lower divi- sion of the system the Stockbridge or J]olian limestone, including the white marbles of Vermont; which, by their organic remains have since been by Billings found to belong to the Levis fovi^. tion. A large portion of the related rocks in western Vermont and elsewhere, which afford a ftiuna now known to be far more ancient than that of the Lower Taconic just referred to, and as low if not lower than anything in the New York system, were, by Emmons, then placed partly near the summit of the Upper Taconic, and partly not only above the whole Taconic system, but above the Champlain division of the New York system. Thus we find in 1842, in his Report on the Geology of the Northern District of New York (where Emmons defined his views on the Taconic system), that he placed above this latter horizon, both the green sandstone of Sillery mar Quebec, and the red sandrock of western Vermont, (which he then regarded as the representatives of the Oneida and the Medina sandstones,) and described the latter as made up from the ruins of Taconic rocks [pages 124, 282]. In 1844-184(), in his Report on the Agri- culture of New York [I. 119], he however adopted a diff"erent view i f the red .sandrock, assigning it to the Calciferous ; and in 1855, in his '' American Geology" [ii. 128], it was regarded as in part Calciferous and in part Potsdam. In 1848 Prof. C. B. AdaniS, then director of the Geological Survey of Vermont, argued strongly against these latter views, and maintained that the red sandrock directly overlaid the .shales of the Hudson- River group and corresponded to the Medina and Clinton forma- tions of the New York system. [Amer. Jour. Sci. TI, v. 108.] He had before this time di.scovered in this sandrock, besides what he considered an Atn/pa, abundant remains of a trilobite, which Hall, in 1847, referred to the genus Conocephufus (J^oito- f :il (lieeiiwieii, New Y'ork. Tliese were by Emmons, in his essay on the Taeonic eysi.em lin i844i, described as characteristic of that system of rocks. A copy of tho Regent's Report for 1850 having been sent by Billings ;.() Barrandc, this eminent paleontologist, in a letter f« MB 38 addressed to Prof. Bronn of Heidelberg, July 16, 1860 [Amer. Jour. Sci. II, xxxi, 212], called attention to the trilobites therein figured, and declared that no paleontologist familiar with the trilobites of Scandinavia would " have hesitated to class them among the species of the primordial fauna, and to place the schists enclosing them in one of the formations containing this fauna. Such is my profound conviction, etc." The letter con- taining this statement had already appeared in the American Journal of Science for March, 1861, but Mr. Billings in his note just referred to, on the fossils of Highgate, in the same Journal for September of that year, makes no allusion to it. In March, 1862, however, he returns to the subject of the sandrock, in a more lengthy communication [Ibid II, xxxiii. 100), and after correcting some omissions in his former note, alludes in the fol- lowing language to Mr. Barrande, and to the expressed opinion of the latter, just quoted, with regard to tlie fossils in question and the rocks containing them : " I must also state that Bar- rande first determined the age of the slates in Georgia, Vermont, holding /■'. Thompsoni and P. Vennotita^uf." He adds " at the time I wrote the note on the Highgate fossils it was not known that these slates were conformably interstratified with the red sj'ndrock. This discovery was made afterwards by the Rev. J. B. Perry and Dr. G. M. Hall of Swanton." Mr. Billings now blames me [Canadian Naturalist, new series, vi, 318] for having written in my address of last year, with regard to the (reorgia trilobites, first described as Olenus by Prof. Hall, thai Barrande " called attention to their primordial character, and thus led to a knowledge of their true stratigraphi- cal horizon." I had always believed that the letter of Barrande and the explicit declaration of Mr. Billings, just quoted, con- tained the whole truth of the matter My attention has since been called to a subsequent note i»y Mr. Billings in May, 18(52, [Ibid II, xxxiii, 421] in which, while asserting that Emmons had already assigned to these rocks a greater age than the New Vork system, he mentions that in sending to Barrande, in the spring of 1860, the llcport of Prof. Hall on the Georgia fossils, he alluded to their primordial character, and suggested that they might belong to what Mr. Barrande has called ' a colony' in the rocks of the second fauna. This is also stated in a note by Sir William Logan in the preface to the Gtiology of Canada [page viii.J As the genus Olenus, to which I'rof. Hallhad referred 39 the fossils in question, was at that time (1860) well-known to belong, both in Great Britain and in Scandinava, to the primordial fauna, Mr. Barrande does not seem to have thought it neces- sary in his correspondence to refer to the very obvious remark of Mr. Billings. Mr. Billings further showed in his paper in March, 1862, that fossils identical with those of the Georgia slates had been found by him in specimens collected by Mr. Richardson of the Geologi- cal Survey of Canada in the summer of 1861, on the J>abrador coast, along the strait of Belisle : where Olenellus (^Parndoxides) Thompsoni and 0. Vermontana were found with Conncoryphe (Co7iocephtdus) in strata which were by Billings referred to the Potsdam group. [See for the further history of these fossils the Geology of Canada, pages 866, 955, and Pal. Fossils of Canada, pages 11, 419.] The interstratification of the dark-colored fossiliferous shales holding Olenellus with the red sandrock of Vermont, announced by Mr. Billings, was further confirmed by Sir William Logan in his account of the section at Swanton, Vermont [Geology of Canada, 281]. They were there declared to occur about 500 feet from the base of a series of 2200 feet of strata, consisting chiefly of red sandy dolomites (the so-called sandrock) contain- ing Conoccphiilus throughout, while the shaly beds held in ad- dition, the two species of Paradoxidea {Olenellus) and some brachiopods. These beds, like those of Labrador, were referred by Logan and by Billings to the Potsdam group. The conclusions here announced were of great importance for the history of the Taconic controversy. The trilubitcs of primordial type, from Georgia, Vermont, which by Emmons were placed in the Taconic system, lying unconformably beneath a series of rocks belonging to the lower part of the New York system, were now declared to belong to the red sandrock group, a member of this overlying system. Mvmli has been said of these fossils, as if they furnished in some way a vindication of the views of Emmous, and of the Taconic system ; a conclusion which can only be deduced from a misconception of the facts in the case. Emmous had, previous to 1860, on lithological and stratigrapliical evidence alone, called the Georgia slates Taconic, and i)laccd them uncuuforiiiably beneath the red sandrock. If now both he and Billings were right in referring the red sandrock to the Calciferous and I'otsdam for- mations, and if the stratigraph'cal determination of JMessrs. Perry !!! 40 and G. M. Hall, confirmed by those of Logan, were correct, viz : that the trilobites in question occur not in a system of strata lying unconformably beneath the red sandrock, but in beds inter- calated with the red sandrock itself, it is clear that these trilo- bites must belong not to the Tac:>uic, but to the New York system. We shall return to the question of the age of these rocks. We have seen that Prof. James Hall, in 1847, and again in 1859, referred trilobites regarded by him as species of Olenus to the Hudson-River group, or in other words to the summit of the second paleozoic fauna, while it is now well known that they are characteristic of the first fauna. In this reference, in 1847, Prof. Hall was justified by the singular errors which we have already pointed out in the works of Hisinger en the geology of Scandi- navia. In his Antickmngfu; in 1828, while the colored map and accompanying sections show the alum-slates with Paraihxides to lie beneath, and the clay-slates with graptolites, above the orthoceratite-limcstoiic, the accompanying colored legend, designed to explain the map and sections, gives these two slates with tlie numbers 3 and 4, as if they were contiguous and beneath the limestone^ which is numbered 5. The student who, in his per- j)lexity, turned from this to the later work of Hisinger, his Lethiiea Suecica, found the two groups of slates, as before, placed in juxtaposition, but assigned, together, to a position above the orthoceratite-limestone. Thus, in either case, he would be led to the conclusion that in Scandinavia the alum-slates with Olenus, Paradoxulcs and Coiwcephalus {Coiiocuri/plie) were closely asso- ciated with the grajitolitic shales ; and, upon the authority of the latter work, that the position of both of these was there above the orthoceratite-limestones, and at the summit of the second fauna. The graptolitic shales of Scandinavia were already identified with those of the Utica and Hudson- River formations of tlic New York system. The red sandrock of Vermont, containing Coiioajjhafus, had been, both by Emmons and Adams, alike on lithological and stratigraphical grounds, referred to the still higher Medina sandstone; a view which, as we have seen, was still main- tained and strongly defended by Adams. This was in 1847, and Angelin's classification of the transition rocks of Scandinavia, fixing the position ol" the various trilobitic zones, did not appear until ISC^t Prof. Hall had therefore at this time the strongest reasons for assigning the rocks containing Olcnns to the summit of the second launa. Before we can understand his reasons for 41 maintaining a similar view in 1859, we must notice the history of geological investigation in eastern Canada. So early as 1827, Dr. Bigsby, to whom North American geology owes so much, had given us [Proc. Geol. Soc. I, 37] a careful description of the geology of Quebec and its vicinity. He there found resting directly upon the ancient gneiss, a nearly horizontal dark colored conchiferous limestone, having sometimes at its base a calcareous conglomerate, and well displayed on the north shore of the St. Lawrence at Montmorenci and Bcauport. He distinguished moreover a third group of rocks, described by him as a " slaty series composed of shale and graywacke, occasionally passing into a brown limestone, and alternating with a calcareous conglom- erate in beds, some of them charged with fossils * * * * derived from the conchiferous limestone." (This fossiliferous conglomerate contained also fragments of clay-slate.) From all these circumstances Bigsby concluded that the flat conchiferous limestones were older than the highly inclined graywacke series ; which latter was described as forming the ridge on which Quebec stands, the north shore to Cape Rouge, the island of Orleans, and the southern or Foint-Levis shore of the St. Lawrence ; where besides trilobites, and the fossils in the conglomerates, he noticed what he called vegetable impressions, supposed to be fucoids. These were the graptolites which, nearly thirty years later, were studied, described and figured for the Geological Survey of Ca- nada by Prof James Hall ; who has shown that two of the spe- cies from this locality were described and figured under the name of fucoids by Ad. Brongniart, in 1828. [Geol. Sur. Canada, Decade II, page GO.] Bigsby, in 1827, conceived that the lime- stones of the north shore might belong to the carboniferous period, and noted the existence of what were called small seams of coal in the graywacke series of the south shore, which sub- stance I have since described in the Geology of Canada [page 525.] In 1842, the Geological Survey of Canada was begun by Sir William Logan, who in a I'rcliminary Report to the Government, ill that year [page 19], says " of the relative age of the contorted rocks of Point Levis, opposite (Quebec, I have not any good evi- dence, though 1 am inclined to the opinion li. t they come out from below the flat limestones of the St. Jjawrence." He how- ever aubse. sericca, and an Orthis, very like 0, tcstudinaria, and taken by me to be these species, being then the only fossils found in the Canadian rocks in question. This view supported Prof. Hall in placing, as he had already done, the Olenus rocks of New York in the Hudson-River group, in accordance with Hisinger's list of Swedish rocks as given in the Lethcea Suecica in 1837, and not as he had previously given it." The concurrent evidence deduced from stratigraphy, from geographical distribution, from lithological and from paleontologi- cal characters, thus led Logan, from the first, to adopt the views already expressed by Bigsby, Emmons and Bayfield, and to assign the whole of the paleozoic rocks of the south-east shore of the St. Lawrence, below Montreal, to a position in the New York system above the Trenton limestone. While thus, as he says, founding his opinion on the stratigraphical evidence obtained in Eastern Canada, Logan was also influent d by the consideration that the rocks in question were continuous with those in western Vermont. Part of the rocks of this region had, as we have seen, originally been placed by Emmons at this horizon, while the others, referred by him to his Taconic system, were maintained by Henry D. Rogers to belong to the Hudson-River group ; a view which was adopted by Mather and by Hall, and strongly defended by Adams, at that time engaged in a Geological Survey of Vermont, with which in 1846 and 1847, the present writer was connected. As regards the subse(juent paleontological discoveries in these ii rocks in Canada, it is to be said that the graptolitcs first noticed by Bigsby in 1827, were re-discovered by the Geological Survey, at Point Ldvis in 1854, and having been placed in the hands of Prof. James Hall, (who in that year first saw the rocks in ques- tion) were partially described by him in a communication to Sir W. E. Logan, dated April, 1855, and subsequently at length in 1858 [Report Gkiol. Survey for 1857, page 109, and Decade II.] They were new forms, it is true, but the horizon of the grap- tolitcs, both in New York and in Sweden, was the same as that already assigned by Logan to the Point-L(5vis rocks. Thus these fossils appeared to sustain his view, and they were accord- ingly described as belonging to the Hudson-River group. Up to 1856, no other organic remains than the graptolites and the two species of brachiopods noticed by Sir William Logan, were known to the Geological Survey as belonging to the Point Ldvis rocks ; the trilobites long before observed by Bigsby not having been re-discovered. In 1856, the present writer, while engaged in a lithological study of the various rocks of Point Ldvis, found in the vicinity of the graptolitic shales, beds of what were described by him in 1857, [Report Geol. Surv. 1853- 56, page 465,] as " fine granular opaque limestones, weathering bluish-gray, and holding in abundance remains of orthoceratites, trilobites, and other fossils ; which are replaced by a yellow- weathering dolomite." In these, which arc. probably what Bigsby had long before described as fossiliferous conglomerates, the dolomitic matter is so arranged as to suggest a resemblance to certain beds which are really couglomerate in character, and were, at the same time, described by me as interstratified with the fossiliferous limestones, and as holding pebbles of pure limestone, of dolomite, and occasionally of quartz and of argillite ; the whole cemented by a yellow-weathering dolomite, and occa- sionally by a nearly pure carbonate of lime. [Ibid 466.] The included fragments of argillite, (previously noticed by Bigsby) which are greeuisli or purplish in color, with lustj'ous surfaces, are precisely similar to those which f(trm great beds in the crys- talline schists of the Green Mountain series of the Appalachian hills, which extend in a north-east and south-west course along the south-eastern bord(!r of the rocks ol' the Quebec group. I conceive that these argillite fragments, (like those in the Potsdam conglomerate near Lake Champlain, referred to in my address of last year,) are derived tiom the ancient schists of the Appal- lachians. 46 This re-disc6Very of fossiliferous limosfcones at Point L^vis led to farther exploration of the locality, and in 1857, and the following years, a large collection of trilobites, brachiopods, and other organic remains was obtained from these limestones by the Geological Survey of Canada. Mr. Billings, who in 1856, had been appointed puleontologist to the Geological Survey, at once commenced the study of these fossils from Point Ldvis, and at length arrived at the important conclusion that the organic; remains there found, belonged not to the summit of the second faiina, but were to be assigned a j)osi- tion in the first or primordial fauna. This conclusion he com- municated to Mr. Barrande in a letter, dated July 12, 18(50, [Amer. Jour. Sci. II, xxxi, 220] and gave descriptions of many of the organic forms in the Canadian Naturalist for the same year. T have already alluded, in describing the rocks of Point L(5vis, to the peculiarities of aspect which probably led Dr. Bigsby, in 1827, to confound these fossiliferous limestones, j»ene- tratod by dolomite, with the true dolomitic conglomerates asso- ciated with them, and helped him to suppose the fossils to be derived from the limestones of the north shore, now known tc» be younger rocks. This mistake was a very natural one at a time when comparative paleontology was unknown. Sir William Logan meanwhile made a careful stratigraphical examination of the rocks of Point Levis, and notwithstanding the peculiarities of the limestones which there contain the pri- mordial fauna, declared himself, in December, 1860, satisfied that " the fossils are of the age of the strata." In consequence of the discovery of Mr. Billings, Logan now proposed to separate from the Hudson-River group the graywacke series of Bigsby and Bayfield, and ascribed to it a much greater antiquity ; regarding it as "a great development of strata about the horizon of the Chazy and Calciferous, brought to the surface by an overturn anticlinal fold, with a crack and a great dislocation run- ning along the summit," by which the rocks in question were "brought to overlap the Hudson-River formation." This series, to which was assigned a thickness of from 5000 to 7000 feet, he named the Quebec group, which included the green sandstones of Sillery, regarded as the summit, the fossiliferous limestones and graptolitic shales at the base, which afterwards received the name of the Levis formation, and a great interme- diate mass of barren shales and sandstones, called the Lauzon 46 formation. The first account of this change in the stratigra- phical views of Logan occurs in his letter to Barrande, dated December 'SUi, 18(50. [Amer. Jour. Sci. II, xxxi, 21(;.J This important distinction once established, it was found ne- cessary to draw a line from the St. Lawrence, near Quebec, to the vicinity of Lake Champlain, separating the true Hudson-River group, with its overlying Oneida or Medina rocks, on the north- west side, from the so-called Quebec group, on the south and east. This division was by Logan ascribed to a continuous dis- location, which had disturbed a great conlbrmable paleozoic series, including the whole of the members of the New York system from the base of the Potsdam to the summit of the Hudson-River group, and, throughout the whole distance of IGO miles, had raised up the lower forniations in a contorted and inclined attitude, and caused them to overlie in many cases the higher formations of the system. This dividing line was by Logan traced north-eastward through the island of Orleans, the waters of the lower St. Lawrence, and along the north shore of Gaspd ; and south-westward through Vermont, across the Hud- sou, as far at least as Virginia; separating, throughout, the rocks of the Quebec and Potsdam groups, with their primordial fauna, from those of the Trenton and Hudson-River groups, with [the second fauna. This is shown in the geological map of eastern America from Virginia to the St. Lawrence, which appears in the Atlas to the Geology of Canada, published in 1865. In an earlier geological map published by Sir William Logan at Paris in 1855, before this distinction had been drawn, the region in question in Eastern Canada is colored partly as the Oneida formation, and partly as the Hudson-River group; while in the accompanying text the Sillery sandstone is spoken of as the equivalent of the Shawangunk grit or Oneida conglo- merate of the New York system. [Esquisse Geologique du Canada; Logan and Sterry Hunt, Paris, 1855, page 51.] These rocks were by Logan traced southwards across the frontier of Canada, into Vermont, where they included the red sandrock and its associated slates ; which were thus by Logan, as well as by Adams, looked upon as occupying a position at the summit of the second fauna. When therefore in 1859, Prof. Hall described the trilobites fhalas found in the Levis rocks are by him compared with those found in the Upper Lin- gula fiags or Dolgelly beds. The graptolitic strata of Levis however clearly represent the Lower Llandeilo or Arenig rocks of North Wales, the Skiddaw group of Sedgwick in Cumberland, the graptolitic beds which in Esthonia, according to Schmidt, are found below the orthoceratite-limestones, |Can. Naturalist, L vi.' 345| and those of Victoria in Australia, [.Mem. Geol. Sur. Ill, part 2, 255, 804.] In the Lower Llandeilo and Upper Trema- doc beds there appears to be in North Wales, a mingling of forms of the first and second faunas, as in the Levis and Chazy formations. The latter was already, by Hall, in 1847, declared to be beneath the Silurian horizon then recognized in Great Brit.iin. By its fauna it is comparatively isolated from the strata both below and above it, and stratigraphically as well as paleontologically it would appear to belong rather than to the lower than to the higher rocks. According to a private communication from Prof. James Hall, the Chazy limestone at Middleville, Herkimer county, New York, to the south of the Adirondacks, is wanting, and the basal beds of the Trenton group (the Birdseye limestone) there rest unconformably upon the Caleiferous saudrock. The relations of the various members of the Quebec group to each other, and of the group, as a whole, to the succeeding IVen- toQ and Hudson-River groups, require further elucidation. If, as I am disposed to believe, the southeastward-dipping series of the older strata near Quebec, exhibits the northwest side of an overturned and eroded anticlinal, in which the normal order of the strata is inverted, then the Lauzon and Sillery divisions, which there appear to overlie the Levis limestones and shales, are older rocks, occupying the position of the Potsdam or still 5G lower inemborp of the Cambrian. Sir William Logan supposes the appearance of these rocks in their present attitude by the side of the strata of the Trenton and Hudson Kivor-groups, in the vicinity of Quebec, to be due to a great dislocation and uplift, subsequent to the deposition of these higher rocks; but, as sug- gested in ray address of last year, 1 conceive the Quebec group to have been in its present upturned and disturbed condition before the deposition of the Trenton limestones. The supposed dislocation and uplift, extending from the gulf of St. Lawrence to Virginia, is according to this view, but the outcrop of the rocks of the first fauna from beneath the unconformably over- lying strata of the second fauna. The later movements along the borders of the Appalachian region have however, to some extent, aifccted these, in their turn, and thus complicated the relations of tlie two series. This unconformity, which corresponds to the marked break between the Levis and Trenton faunas, is farther shown by the stratigraphical break and discordance in Herkimer county. New York ; and by the fact th;it beyond the limits of the Ottawa bisin, on eitlicr side, the limestone of the Trenton group rests directly on the crystalline rocks ; the older members of the New York system being altogether absent at the northern outcrop, as well as in the outliers of Trenton limestone seen to the north of Lake Ontario, and as far to the north-east as Lake St. John on the Saguenay. This distribution shows that a considerable movement, just previous to the Trenton period, took place both to the west and tlie east of the Adirondack region, which formed the soutliern boundary of the Ottawa ba-nn. The Levis and Chazy formations, as we have seen, offer a conmiingling of forms of the first and second faunas, which shows them to behmg to a p(>riod of transition between the two ; but it is remarkable that so fir as yet observed, no representatives of the later of these faunas are knc 'n to the east and south of the Appalachians, along the Atlantic coast ; the first fauna, whether in Massachusetts, New Brunswick or southeastern Newfound- land, being unaccompanied by any forms of the second. The third fauna, on the contrary, is represented in various localities both within and to the east of the Appalachian region, from Massachusetts to Newl'oundland. In parts of Gasp(?, and also in Nova Scotia, strata holding forms referred to the Clinton and Niagara divisions are met with, as well as other beds of Lower Helderberg age, associiited with species of shells and of plants i _4 m It which connect this fiiuuu with that of tlic succeeding Lower Devonian or Erisin period. To thiw Lower Helderbor<>; horizon (corrcs|)ondin, S,,strm or in the various editions oWSi/nru, or by Kan.say, who however speaks of the Llandovery rocks as an intermediate series, (Mem. r.eol. Survey III, part 2, page 2.) Inasmuch as the name of Silurian was erroneously applied to the rocks of the second fauna, and pro- perly belongs to those of the third fauna only, thnt of Middle Silurian should be rejected from our nomenclature in North America, as has already been done in England. The strata to which it has been applied, on both sides of the Atlantic, are how- ever important as illustrations of the passage from one fauna to another. The history of the introduction (.f the names of Silurian and Devonian into North American geology demands our notice. Prof. Hall, as we have seen, while recognizing in the rocks of the New York system the representatives alike of the British Cambrian, Silurian and Devonian, wisely refrained from adopt- ing this nomenclatun-, n, the bases of paleozoio geology. — {From the Canadian Naturalist /or April midJidy 1872.) ' r ■