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Mapa, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely Included in one exposure ara filmed beginning In the upper left hand comer, left to right and top to bottom, aa many frames aa required. The following diagrams iilustrate the method: Lea cartea, planchea, tabiaiiux, etc., peuvent itre filmie A dee taux d9 rMuction diff^rents. Lorsque le document est trop grand pour dtre reproduit en un seui cliche, ii est film* A partir de I'angle supAriaur gauche, de gauche h droite, et da haut en baa, an prenant le nombre d'imagea nAcaasaira. Laa diagrammea suivants illustrent ia mithoda. 32X 1 2 3 1 2 3 4 5 6 IMPRESSIONS AND FOOTPRINTS OF AQUATIC ANIMALS AND IMITATIVE MARKINGS, ON CARBONIFEROUS ROCKS. By J. W. DAWSON, LL. D., F. R. S. Ml [Fboh thk Ameeioan Journal op Science and Arts, Vol. V, Jan., 1873.] IMPRESSIONS km FOOTPRINTS OF AQUATIC ANIMALS AND IMITATIVE MARKINGS, ON CARBONIFEROUS ROCKS. By J. W. DAWSON, LL.D., F.R.S. / The footprints and other markings of aquatic invertebrate animals and of fishes are necessarily, for the most part, less distinctive and important than those of land animals, both because less characteristic in themselves, and because reproduced under similar forms in very different geological periods. The former peculiarity has caused them to be neglected as of little importance, or to be confounded with impressions of plants. With reference to the latter, I have myself shown that the impressions made by the modern King-crab faithfully represent tie Protichniies, Climactichm'tes, and Rxisichnites of the Primor- dial and Silurian, and similar comparisons have been made by Salter, Jones, Dana and others, between the tracks of modern Crustaceans and worms and some of those in the oldest rocks. 1. Protichniies Owen. The footprints from the Potsdam Sandstone in Canada, for which this name v^as proposed by Owen, and which were by him referred to Crustaceans probably resembling Limulus, were 2 J. ir. Dawson — FoolpriiiLs^ etc.^ on Carboniferous Rocks. shown by me in 1862* to correspond precisely with those of the American Liniuhis {Pvlyphemus occidental is). I proved by experiment with the modern unimal that the recurring series of groups of markings were produced by the toes of the large posterior thoracic feet, the irregular scratches seen in Protichnites lineatus by the ordinary feet, and the central furrow by the tail. It was also shown that when the Limulus uses its swimming lieet it produces impressions of the character of those named Climac- tic/mites, from the same beds which afford Protichnites. I^he principal difference between Protichnites and their modern representatives is that the latter have two lateral furrows pro- duced by the sides of the (sarapace, which are wanting in the former. As Limuloid crustaceans are well knov»'n in the Carbonif- erous beds of Europe and America, their footprints might be expected to occur in rocks of this age, but the first I have met with were sent to me last summer by my friend Mr. Elder, of Harvard College, who found them quite abundantly in dark- colored flag-stones belonging to the Millstone Grit formation at McKay's Head in Nova Scotia (fig. 1). The animal which pro- duced these marks must have been of small size (about half an inch in breadth), in this agreeing with the usual size of the Coal-formation Limuloids; and like the ancient Protichnite- makers, it left no trace of the edges of the carapace, but a very distinct impression of a sharp pointed tail. Its posterior fieet had three or possibly four sharp toes. There were besides several pairs of sharp-pointed walking feet. On the same slabs there are some series of marks, evidently made by the same kind of animal, which have no tail-mark, and there are tail- mai'ks with only traces of those of the toes. It is worthy of notice that, though these tracks indicate the presence of the ani- nials, no crusts of Carboniferous Limuloid crustaceans have yet been found in Nova Scotia. The sand in which the tracks now referred to were made was probably too hard to pennit the swimming feet to make any impression. With respeci; to the absence of the marks of the sides of the carapace, I may ob- serve that the genus Belinurus of the Carboniferous had the sides of the carapace less deep than that of the modern Limu- lus, and this may also have been the case with the more ancient Limuloids of the Potsdam. See as to this a letter bv Prof. Hall in the Canadian Naturalist, 1862. To Protichnites may perhaps be referred a very singular impression from Horton Bluff (fig. 2), which at first sight much resembles P. Scoiicus, from the Primordial of Eoxburghshire, though the Carboniferous specimen is larger and more compli- cated.t It seems to have been produced by the successive * Canadian Nat., vol. vii. • f Siluria, 4th edition, p. 15S. i t J. W. Dawson — Footp-mts, etc., on Carhonijerous liochs. 8 pressure of a pair of flat organs, crenated or toothed at the edges, rather than divided into separate toes. Its horizon is the Lower Carbon iferons. It was eollected by Prot! Hartt The first speeies of Protichuites referred to above may be aj)propriately named P. I'arhmiarius, and the second P. Acadicus. Tliey ,are, I believe, the first impressions of this kind lound in the Carboniferous. 2. Rusic/mites Dawson. In a paper published in the Canadian Naturalist, 18H4, I showed that the singular bilobate markings with transverse striae named Riisopliyciis by Hall, and found in the Chazy of Canada and the Clinton group of New York, are really casts of burrows coimected with footprints consisting of a double series of transverse markings, and that a comparison of them with the trails and burrows of Limulus justified the conclusion that they were produced by Trilobites. I proposed for these and for similar impressions of small size found in the Carboniferous, the name given above. The Carboniferous examples I supposed might have been produced by the species of Philllpda found in these beds. A specimen recently obtained from Horton shows this kind of impression passing in places into a kind of Pro- tichnites, as if the creature possessed walking feet as well as the lamellate swimming feet which it ordinarily used. I can scarcely doubt that the Cruziana semiplicata of Salter, and C. similis of Billings from the Primordial of Newfound- land, must have been produced by crustaceans not dissimilar from those to which Rusichnites belongs. To Rusichnites rather than to Proticlmites ought perhaps to be referred certain transverse linear impressions with a broad central groove from the Lower Carboniferous of Horton, which occur at that place under dili'erent modifications, and sometimes seem to change into light scratches or touches of feet employed in swimming, or end abruptly as if the animal had suddenly risen from the bottom. Arenicoliies Salter. This genus may be held to include cylindrical burrows of , worms with or without marks of minute setae. They occur in Vocks of all ages, and are especiallj' abundant in the Lower Carboniferous series of Half-way Kiver, Nova Scotia, and in the Upper Coal-formation at Tatamagouche in the same province ; those at the latter place showing minute scratches produced by the setffi of the- worms.* With the ordinary form at Horton there occur very long and slender, thread-like forms of the same nature with those to which the name Nemertites has been given. * Journal of the Geological Society, vol. ii. 4 'J. W. Dawson — Footpri/its,t;tc., un (lirhtiniferons Rock.t. 1 liiivo long been of opinion timt iniiny of the cylinilrical markinjrs vvhieli liave been described as plants under the names Pahfochofda, fint/iotirphis, Pakeophycus, Art/irop/ii/cus, &e,, are bnrrovvs of this kind, but tiie main ditHeulty seemed to be to account for their branching in a radiate or palmate manner. I have rec(!ntly nn^t with specimens from the Primordial and Carboniferous which seem to explain this. They show a cen- tral hole or burrow from which the animal seems to have stretched and withdrawn its body in different directions, so as to give an appearance of branching and radiation, possibly due merely to the excursions of the same worm from the mouth of its burrow. No distinct examples of the Primordial and Silurian worm- trails known as Nneites, Myrianites and Crusisopodia, have yet occurred to me in the Carboniferous. DiplicJi n ites Daw son . In the Journal of the Geological Society for 1861, 1 described a remarkable series of imj)ressions found at the Joggins in the Coal-formation, on the surface of a sandstone holding foot- prints of reptiles. It consists of two rows of strongly marked depressions about one inch long and a quarter of an inch broad (fig. 3). These marks are placed close together in each row, and the rows are six inches apart, while the space between is somewhat smoothed as if by a flat body drawii over it. The general appearance is somewhat that which would be produced by a heavy-laden toy cart six inches wide, and with broad wheels, notched or cogged at the edges, if dragged over firm sand. I suggested, in the paper above mentioned, that these singular markings might have been produced by a large crus- tacean or by a gigantic worm, or by a serpentiform batrachian. I have since found a very perfect but smaller series on a sand- stone of the Upper Coal-formation near Toney river, which in the varying distances of the impressions seems to show that they were made by prominent movable points, while the absence of any mark or smoothing between the rows shows that the body of the animal was bonie above the sand. I have hence been induced to suppose that these imprints may have been produced by the pectoral or ventral fins of fishes armed with strong spines, on which the creatures may have executed a sort of walking movement when in shallow water. In my col- lection from the Joggins there is a spine which I have figured and described in my Acadian Geology under the name Uyra- canthus duplicatus, which if we can suppose it to have been a pectoral or ventral spine, would produce precisely such impres- sions as those of the smaller series above mentioned. The r ti t r ti X J. \V. Datoaon — Footprints, etc, on Carbani/erous Rocks, 6 impressions of the type of Diplicihtiite:^ are known to me only in the C/arlx)niferous. Sn'riehiilt<'.> ol" Hillings, i'roni the Anti- costi group,* has some points of reseml)lanc'e to it, hut is essen- tially distinct. My species may he named I), irm'yma. RabiUchniie.s Dawson. Under this name I would designate the straight or slightly curved marks usually striated or grooved h)ngitur trailed over it Some of the beds at Horton Bluff are as completely striated in this way as if glaci- ated, only that the stj'iae are individually more definite and are in all directions. It is worthy of note that these markings strikingly resemble the so-called Eophyton described by Torell from the Primordial of Sweden, and by Billings from that of Newfoundland ; and which also occurs abundantly in the Primordial of New Bruns- wick, After examining a series of these markings from Swe- den shown to me by Mr. Carruthers in London, and also speci- mens from Newfoundland and a large number in situ at St John, I am convinced that they cannot be plants, but must be markings of the nature of Rabdichnites. This conclusion is based on the absence of Carbonaceous matter, the intimate union of the markings with the surface of the stone, their indef- inite forms, their want of nodes or appendages, and their mark-, ings being always of such a nature as could be produced by scratches of a sbarp instrument Since, however, fishes are yet unknown in beds of this age, they may possibly be referred to the feet or spinous tails of swimming crustaceans. Salter has already suggested this origin for some scratches of somewhat different form found in the Primordial of Great Britain. He * lieport on Silurian Fossils of Anticosti, 1866. 6 ♦/. W. Daioson — Footjtrinls^ etc., on Ccirhoniffroiis Hocks. suppo.sed them t(i have beeii the work of s|K!t!ies of Hyinenova- rin. TlicHe murks may, liovvover, indieatc the existence of some free-swimming animiils of the Primordial seas as yet unknown to us. Three otiier suggestions nu'iit eonsideration in thisconneetion. One is that algie and also land plants, drifting with tides or cur- rents, often make the most remarkable and fantastic trails. A marking of this kind was observed by Mr, (I. M. Dawson last summer to be produced by a Laminaria, and in complexity it resembled the extraordinary /Kitujiiiichnus vm/li/'onnis of Hitch- cock from the Connecticut sandstones. Much more simple markings of this kind would sullice to give species of E'opfiij- ton. Another is furnished by a fact stated to the author by Prof. Morse, namely, that LinguUe, when dislodged from their burrows, trail themselves over the bottom like worms, by means of their cirri. Colonies of these creatures, so abundant in the Primordial, may, v;hen obliged to remove, have covered the surfaces of V)eds of mud with vermicular markings. The third is that the Rabdichnite-markings resemble some of the grooves in Silurian rocks which liav been referred to trails of Gastero- pods, as for instance, those from the Clinton group, described by Eiall. As might be expected, the markings above referred to, when in relief, occur on the under sides of the beds. A few instances may, however, be found where they exist on the upper sur- faces. On careful consideration of these raised impressions, I have arrived at the conclusion that they have been left by denu- dation of the surrounding material, just as footprints on dry snow sometimes remain in relief after the surrounding loose snow has been drifted away by the wind; the portion consoli- dated by pressure being better able to resist the denuding agency. Such markings in relief on the upper surfaces of beds are, however, I believe, altogether exceptional. It seems idle to give specific names to markings of this kind. They have evidently been made b^ many ditYerent species of animals, but they afford no certani characters. Fig. 4 a to/ represents some of the forms most common in the Carboniferous beds. Imitative Markings. Bill-marks are often yevy beautifully developed on the Car- boniferous shales and argillaceous sandstones, though not more elaborately than on the modern mud-banks of the Bay of Fundy,* and they occur as far back as the oldest Cambrian.f Some of these simulate leaves of ferns and fronds of Laminariae, * Acadian Geology, 2nd ed., p. 26. f Salter, Journal of Geol. Society, vol. xii, p. 251. i 1 i 1 i I i 1 ./. [V. Dnwmn — Footprints^ etc., on Carhoniffroun Roch. 7 and otlierH reHctriMo rootH, fucoidw allied to Hutliotrephis, or the radiating worni-lmrrow.s ulready referred to. SJirinlcwjti c.mrks are also abiuulant in Morncu)! the Cari)onifer- ous beds and iire soiu«!tiines accornijunied with iinprtissions of rain-dropM. When tinely reticidatecl they u\\\i}\\ l»e inintaken for the vonati(jn ol leaves, and when t'otn|")li<'ated with little rill- marks trilmtarv to their sidt!s, they precisely resemble the Die- tnolites of liall from the Medina ►Sandstone. An entirely dillerent kind of shriiikage-eraek is that whieh occurs in certain earbonized and flattened plants, and which sometimes communicates to them a marvelous resend)lance to the netted un(l(n--surfaee of an exogenous leaf (fig. 6). Flat- tened stems of plants and layers of (tortieal nuitter, when car- bonized, shrink in su(;h a maimer as to produce minute reticu- lated cracks. IMiese become (illed with mineral matter before the (!oaly substance has been completely consolidated. A fur- ther compression occurs, causing the coaly substance to collapse, leaving the little veins of harder mineral matter projecting. These impress their form uj)on the clay or shale above and beh)w, and thus when the mass is broken open we have a '^ar- bonaceous film or I'lin layer covered with a network of raised lines, and corresponding minute depressed lines on the shale in contact with it. The reticulations are generally irregular, but sometimes they very closely resemble the veins of a reticu- lately veined leaf. One of the most curious specimens in my possession was collecte>l by Mr, Elder in the Ijower Carbon- iferous of Ilorton Bluff. Tlie little veins which form the pro- jecting network are in this case white caleite ; but at the sur- face their })rojecting edges are blackened with a carbonaceous film. Slicken-slded bodies^ resembling the fossil fruits described by Geinitz as Gii/ielmites, and the objects believed by Fleming and, Carruthers* to be casts of cavities tilled with fluid, abound in the shales of the Carboniferous and Devonian. They are, no doubt, in most cases the results of the pressure and consolida- tion of the clay around small solid bodies, whether organic, fragmentary or concretionary. They are, in short, local slicken- sides precisely similar to those found so plentifully in the coal under-clays, and whichj as I have elsewhere f shown, resulted from the internal giving way and slipping of the mass as the " roots of Stiginaria decayed within it. Most collectors of fossil plants in the older formations must, I persume, be familiar with appearances of this kind in connection with small stems, petioles, fragments of wood, and carpohtes. I have in my collection petioles of ferns and fruits of the genus Trigonocarpum partially * Journal of (Jeol. Society, June, 1871. t Ibid, vol. X, p. 14. 8 J. W. Dawson — Footprints, etc., on Carboniferour Backs. Pig. 1, Pmtichnites Carbonarius (nat. size). Carboniferous, Nova Scotia. Pig. 2. — P. Acadicus, " " Pig, 3. — Diplichnites mnigma (reduced). " " Pig. 4. — RaJjdkhnites, different forms (nat. %\7r). " " rig. 5. Carbonized plant with reticulated, markings (nat. size) ; a, enlarged sec- tion oJE part of the same. Carboniferous, Nova Scotia. .ir ■+ 4i ^t 1 4 i • r ^ J. W. Dawson — Footprints, etc., on, Carhoni/erous Rocks. 9 slicken-sided in this way, and which if wholly covered by this kind of marking could scarcely have been recognized. I have figured bodies of this kind in figs. 126 and 231 of my report on the Devonian and Upper Silurian plants, believing them, owing to their carbonaceous covering, to be probably slicken-sided fruits, though of uncertain nature. In every case I think these bodies must have had a solid nucleus of some sort, as the severe pressure implied in slicken-siding is quite incompatible with a mere ''fluid-cavity," even supposing this to have existed. Prof Marsh has well explained anotherphaseof the influence of hard bodies in producing partial shcken-sidcs, in liis paper on Stylolites, read before the American Association in 1867, and the application of the combined forces of cont^retionary action and slicken-siding to the production of the cone-in-conc concre- tions, which occur in the Coal-formation and as low as the Pri- mordial, was illustrated bv the author in his Acadian (reologv, p. 676. Of course, as I have not seen the specimens referred by Prof Geinitz to Gulielmites, but only the figures in his Memoir on the Permian plants of Saxony, I cannot otter any decided opin- ion as to their nature ; but I have little doubt that the bodies mentioned by Mr. Carruthers are of the kind above referred to, and would be found to liave had a solid nucleus either (n-ganic or of some other kind. I may remark in conclusion that it would be well if collectors would give some attention to imitative markings and animal footprints of the kinds abo e referred to, as well as to their mode of occurrence with reference to the surfaces and material of the beds on which they are found. The labors of Hitchcock and others show how much interesting information may thus be obtained, and many mischievous errors might also be avoided. En my own studies in fossil botany, I have made it a })oint to collect and study all markings resembling plants, as well as the effects of crumpling, pressure, concretionary action, crystaliza- tion, shrinkage and slicken-siding upon actual vegetable re- mains ; and by so doing I have avoided the trouble and expense of describing and figuring some dozens of imaginary speeies-; while it would be easy to point out in works of some pretension costly figures and elaborate descriptions based on imitative forms or distorted and otherwise altered fossils. iec-