^^^ ^ AUTHORS EDITION. COMPLIMENTS OF TilK AUTHOR Alcatraz Island, San Francisco. Cal, NOTES PAL/EOZOIC CRUSTACE/E NO 2. UN THE NORTH AMERICAN SPECIES OF THE GENUS AGNOSTUS, (From The American Gcoloijist, Vol. i I' 1892) MINNEAPOLIS, JUNE, 1892. [Notes on Palaeozoic Crustacew No. 2.] ON THE NORTH AMERICAN SPECIES OF THE GENUS AGNOSTUS. By A. W. VoGDEs, Fort Canby, Wash. {Fi'om The American Geologist, Vol. IX, June, 1892.'] [Notes on Pnhmzoic CrustaceiV No. 2.] * ON THE NORTH AMERICAN SPECIES OF THE GENUS AGNOSTUS. By A. W, VoGDEs, Fort Canby, Wash. HISTORICAL SKETCH OF THE GENUS AGNOSTUS. The earliest known species of this genus was described and figured by Bromell in 1729, Lithographia Siiecana, Actis Liter., Suecia3, Upsal, vol. 2, p. 527, under the name of Vermiculi vagipenneg. The author mis- takes the fossil for an insect and figures Agnostvs pisiformis from the Olenus schist of Andrarum, Sweden. For a period of almost one hundred years this was the only representative of a genus, to which Brongniart gave the name of Agnostus, taking for its type Agnostvs pisi- formis from Linn^'s Entomolithus pisiformis, Syst. Nat. Ed. xii, p. 160. Dalman uses the same species for the type of his new genus Battus in 1826, Paheaden p. 257. In the 5^ear 1828, Dalman, Vetensk, Akad, Arsber, p. 136, described a new species from Gothland under the name of Battus Imvigatus, and a new variety from Andrarum, as Battus pisiformis var. spiniger. The next contribution to our knowledge of this genus was made by Beyrich in 1845, Ueber Bohm Trilobiten, p. 44. The author adds two new species to the list from the Paradoxides zone of Bohemia, under the *No. 1 of these notes is published in Trans. St. Louis Acad. Sci., Vol, V, 1891. 378 The Araerican Geologist. June, 1 names of Battus nudus and B. integer. The discovery of an entire speci- men by this author removed the doubts regarding the affinities of these fossils with the order Trilobita. The investigations made by M'Coy in 1846, Syn. Silurian Fossils of Ireland, p. 56, added the new genus TrinoduH and one new species, T. agnostiformu. The non-adoption by palaeontologists of Tvinodus, and the imperfect illustration of this species have caused several identical forms to be classed under new names such as Agnostus convexus Salt. A. trinodus Salt, and A. tardus Salt., Brit. Pal. Foss. 1851, p. 141 (not Bar- rande's species). The species ranges high up in the geolog-c column as it approaches its extinction, in the zone with the genus Asaphus and Trinucleus. Barrande described in his Preliminary work on the Silurian System of Bohemia, 1846, pp. 14 and 35, nine new species under this genus; which he reduces to six in his final great work on the Bohemian trilo- bites. Etage C with Parddoxides hoheiidciu contains — Agnostus integer Beyr., A. granulatusBa.TT., A. nudus Beyr.^ A. hibuUutus Barr. and A. rex Barr. Etage D with Asiq^ltus nob ills contains Agnostus tardus Barr. Corda, Prodrom 1847, reclassifies the genus into seven new genera and 29 species. All the genera and species have been referred to well known Bohemian species and genera. In the Mem. Geol. survey, vol. 2, part 1, p. 351, pi. 8, Salter & Phillips reproduce under the name of Agnostus trinodus the Irish species which M'Coy described as Trinodus agnostiforuiis. The authors also describe a variety of this species as connexus. 1851 — Angelin describes and figures 12 species from Sweden, Pahieont. Scand., p. 5, pi 6. Regie A (Olenus zone). Agnostus 'jnsiforrnis Linn^, A. IcBvigatus Dalm., A. reticulatus Aug., Regio B (Paradox ides forchham- meri zone), Agnostus planieauda Aug., A. exscu.lptus Aug., A. punctuosus Ang., A. aculentus Ang.. A. hrenifrons Ang., A. glandiformis Ang., A. bituber- culatus Aug., Regio C (Asaphus zi me), Agnostus lent if orru is Aug., Regio D., Agnostus glabratus Ang. The first North American contribution to Agnostus was made by Bil- lings in 1860, Canadian Nat., vol. 5, p. 302, in which he describes from the so-called Quebec group, three new species, Agnostus americanus, A. ■ orion and A. canadensis. These species are republished in Pa];i!Ozoic Fossils of Canada, vol. 1,1865, p. 395. Agnostus (imericunus is of the type Longifrontes, congeneric with A. trisectus Salt, which occurs at An- drarum with Peltura and SpJucrophthalrnus. A. orion differs from A.pisi- formis by having the glabella proportionally shorter. Tlie same name was used by Barrande in 1846 for a species of the genus. 1860 — Eichwald, Lethea Rossica, vol. 1, p. 1351, The author describes four species, two of which are for the first time illustrated — Agnostus para- doxus Eichw. and .4. nodiger, n. sp. Eichwald refers A. boeckii to A. exseulptus Ang. The two new species are from the Asaphus zone. 1863 — An important contribution to American paleontology was pub- lished during this year by James Hall; entitled Preliminary notice of the fauna of the Potsdam Sandstone, 16th Report N. Y. State Cab. Nat. The American Geologist. Vol. IX, Plate IX. NORTH AMERICAN SPECIES OF AONOSTUS. Genus Agnostics. — Yogdes. 379 Hist. The memoir describes the fossils of the Dikel»cephalus zone of Wisconsin. In this work we have illustrations and descriptions of Agnostus josepha, A. parilis and A. disparilis. The first species ap- proaches A. cyclopyge Tull. of the Olenus zone of Sweden. The second is of the type Lsevigati of which A. Un-igatus Dalm. is its nearest congen- eric form. Dr. Shumard described in the Am. Jour. Sci., vol. 32, 1861, p. 218, Agnostus coloradensis from Burnet county,. Texas. This species is of the type A. neron H. & W. 1864 — Salter in the Mem. Geol. Survey, Decade XI, describes five new species of the genus as follows: Agnostus p>rinceps alsovars. ornatus ard 7'udis (Olenus zone). (This species is of the type A. atauus, gihhus, punc- tuosus, ainericanus), Agnostus maccoyii. Upper Llandeilo Flags, Wales, A. limbatus, Caradoc, A. morea, Lower Llandeilo, A. tj-itiodus, syn. of A. agnostiformis M'Coy, A. trisectus, Upper Lingula. (This species occurs at Andrarum with PeUura2Jid.SpTnerophthalrnus). 1865 — Billings in the Palaeozoic Fossils of Canada, vol. 1, redescribes A. (onericanus, A, orion and A. canadensis. The author adds two new spe- cies to the list from the so-called Quebec group of Newfoundland, Agnostus galha, and A. fahicus. The former species differs but slightly from A. tardus Barr., Etage D, in Bohemia. The latter approaches A. lentiformis Ang., Kegio C, of Sweden. 1866 — Schmidt describes a new species in the Bull. Acad. Sci., St. Petersb , vol. 30, 1866, p. 505, fig. 45, Agnostus cyckanoicskii. 1866— Linnarsson describes a new species in Om de Siluriska bildnin- garne i Mellersta ^Vestergotland; Agnostus affinis from the zone with Paradoxides tessini. 1867 — Belt in the Geol. Mag., vol. 4, p. 294, describes Agnostus nodosus and .4. pisiformis var. obesus, from the "Upper Cambrian" of Wales. Tullberg remarks that A. nodosus Belt is probably identical with A. re- ticulatus Ang. The author illustrates a broad and narrow form of A. pisiformis var. obesus. In vol. 5, 1868, of the same inagazine, the author describes Agnostus obtusus from the Upper Dolgelly and A. harlowii from the Tremadoc. 1868 — Barrande describes Agnostus bavaricus, in Fauna Silurienne des environs de Hoff en Baviere, p. 32, figs. 46-47. 1869 — Linnarsson, Om Vestergotland Camb. «& Sil. aflagringar. The author describes 8 species of Agnostus including the following new species, A. gibbus, A. 2)arvifroas^ A. sidenbladhi, and A. fallax. The first two species occur with Paradoxides tessini at Andrarum. Agnostus sidenbladhi ranges higher up in ihe Ceratopyge chalk. Sjogren in Om nagra forsteningar i Oland Kambriska lager 1871, de- scribes Agnostus regius from the zone with Paradoxides olandicus. 1871— Hicks in the Quart. Jour. Geol. Soc, vol.27, 1^1, p. 400, de- scribes a new species, Agnostus cambriensis. 1872— Meek in the sixth Report U. S. Geol. Sur. Territories, p. 664, gives the name of Agnostus maladensis to a species from Malade City,. Utah; and that of Agnostus bidens to one from Gallatin City, Montana. 1872— Hicks in the Quart. Jour. Geol. Soc, vol. 28, 1872, p. 174, de- 380 The American Geologist. june,i8j« scribes five species, illustrating a new one under the name of Agnos- tus eskriggei from near Dolgelly, Wales. This article also contains de- scriptions of Agnostus davicUs Salt., A scutaUs Salt., A. scarceoides Salt, and A. harrandei Salt. 1872 — Ford illustrates an imperfect trilobite under the name of Ag- nostus nohilis in the Amer. Jour. Sci., vol. 3, 1872, p. 421. This species is from the Olenellus zone near Troy, New York, and may prove to be a species of the genus Microdiscus^ which occurs in the same locality. 1872 — Barrande describes three new species from Etage D, in the Supplement Syst. Sil. Bohm., vol. 1, 18T2: Agnostus caducus, A. perruga- tus and A. similaris. 1876— Kayser, Beitnige zur. Geol. «fe Paheont. der Argentinischen Re- publik, p. 5. The author describes Agnostus tilcuryensis from the Olenus zone. 1877 — White in his Preliminary Report for 1874, also in the final Re- port U. S. Geol. Sur., west 100th Mer., vol. 4, 1877, describes Agnostus in- terstridus from Antelope Springs, Utah. This species is related to A. integer Beyr. Hall & Whitfield in U. S. Geol. Sur. 40th Par., vol. 4, 1877, describe four new species from the Dikelocephalus zone of Nevada: Agnostus communis^ A. neon, A. prolongus, A. tmiddosus. 1878 — Hartt, in Dawson's Acadian Geology, 2d Edition, describes A. acadicus and A. similis ; the latter species is now included as a synonym of A. acadicus. 1878— Brogger, Om Paradoxide^skifrene ved Krekling, describes 14 species including the following new forms, Agnostus gihhus var. hyhrida A. JijenUJi, A. natliorsti, A. incertus, A. pavifrons var. mammilata, also var. nepos, A. nudus var. marginntas, A. p^unctuosus var. ajfinis and A. trunca- tes. All these species occur in the Paradoxides zone. 1880 — Tullberg, in his excellent monograph on the Agnostus species in the Cambrian formation at Andrarum, illustrates and describes 28 species of this genus with the following new species: Group Longi- frons — Agnostus fissus Lund,MSS., A. atavus, A. intermedius, A. elegans^ A. lundgre?ii, A. cyclopyge, A. pusillus. Group Ltievigati — A. cicer. Group Limbati — A. quadratus. Dames in Richthofin's China, vol. 4, p. 27, pi. 2, describes Agnostu» chinensis from the Olenus zone. 1882— Holm, in Kongl. Svenska vet. Akad. Handl., vol. 6, No. 9, de- scribes A. torquisti. 1884— Walcott in Pahi?ont. Eureka Dist. describes six species includ- ing two new species: Agnostus seclusus and A. richmondensis. The first species is of the type A. parvifrons Linrs. and the second of A. natliorsti Brogger. 1885— Matthew in the Trans. Roy. J^oc. Canada, vol. 3, describes 10 species from the Paradoxides zone of St. John: Agnostus regulus, A. partihus, A. vir, also var concinnus, A. acadicus Hartt, var. decliris, A. tes- sella, A. umbo, A. ohtusilohus and A. acutilohus. Genus Agnostits. — Vogdes. 381 1889— Walcott describes in the Proc. Natl. Mus. vol. 12, 1889, the only known American Olenellus zone Agnostus, under the name of A. desid- emtus, from Salem, New York. This species is illustrated in the 10th Report U. S. Geol. Survey, p. 630, pi. 80, fig. 5. RECAPITULATION * From the Olenellus zone, Agnostus nobilis Ford, A. desider- atus Walcott, A. fallax Liurs 3 From the Paradoxides zone 44 From the Olenus zone 6 From the Dikelocephalus zone 19 From the Asaphus zone 18 ~9U AGNOSTUS, Brongniart, 1822. Diagnosis. — The general form of the body of the Agnosti is elongated elliptical, the surface convex. The head presents the same structure as that part in other trilobites, with the exception of eyes and facial suture, which are wanting in this genus. The glabella determined by the dorsal grooves, never extends to the anterior contour; it is always prominent by its relief; its form varies with the species. The typical form has a glabella divided into a small frontal lobe, and a larger posterior lobe; the basal lobes forming a third part. The frontal lobe is usually subtrian- gular having a groove in front {A. pisiforniis, plate ix, fig. 14), In the section Limbati, the glabella is broadly rounded in front, showing a great development as in ^4. rex, plate x, fig. 13. In the section Parvifrontes, the glabella has only a single lobe, as in A. parvifrons, plate x, fig. 12. In the typical glabella the pos- terior lobe exhibits an inclination to divide laterally, or in front, being marked by a medium ridge. The glabella is sometimes compressed on the sides by the basal lobes, but expands at this point again in its posterior projection, as in A. gihJnis. The basal lobes are very short, so that in A. gibbus, they appear like a narrow band widening out on both sides of the head, forming two nodes, which are sometimes large and triangular, as in the section Fallaces. The basal lobes are divided in some species into two nodes on each side, as in A. atavus, but, they are gener- ally very minute. The occipital groove and ring are more or less developed. The lateral lobes of the head form a concentric band with the contour; this is called by Barrande the genal zone. In the section Longifrontes, the cheeks in front of the glabella are divided by a furrow extending from the apex of the glabella to *The varieties are omitted in this enumeration. 382 The American Geologist. June, 1892 the limb. The surface of the genal zone is smooth in the section Limbati, but, in Longifrontes they show a tendency to striate or punctate. The limb around the head is always wider in front and narrowed towards the thorax. One can distinguish upon its surface an internal groove, and an external ridge forming the contour, sometimes the limb is extended into small points on each side, as in A. josepha. In the section Lsevigati the limb becomes obso- lete; in the section Limbati it is broad. The thorax has two segments in all the know^n species. The axis is usually well de- veloped in width, whereas the pleurae are often reduced; when the trilobation is distinct, as in A. rex, the thorax shows the same characteristic; when it is faint, as in A. muUs, the triloba- tion is also indistinct. The first segment is subdivided b}' a groove w^hich gives to the pleurae two bands more or less elevated, the anterior band being the larger; the second segment has the pleurae on each side divided into bands of equal width; the points of each pleura? are directed forward. The pygidium con- forms to the head. In certain species, for example A. hilmUatus^ the pygidium is marked with dorsal grooves; but the head show& no trace of these grooves. In A. rex the axis of the p3'gidium reproduces that of the thorax. The lateral lobes form a concen- tric zone to the contour sometimes united, but often separated behind the axis. The limb surrounding the pygidium is some- times extended into points. If tlie head has no border, that of the pygidium is augmented as in A. nudis. The t3'pical axis occupies generally f of the total length. In front of the axis is located a small triangular border (genou articulaire). The axis has three joints; the center lobe is usually the smallest, but at- tains the greatest hight ; it carries typically on the medium line a node, which sometimes is extended backwards over the third joint (-1. nathorsH and A. acnJcafus), also extended into a spine in A. gihhns. In A. rex the middle joint on the axis is divided by a groove, into an upper and lower lobe. The anterior joint of the axis has an inclination to become separated into three lobes; the two side lobes are common. The last joint is heart- shaped. ' In ^4. rex the last joint is short and rounded; in A. cyclopyge it is large and rounded. Sometimes the axis is long, A. fallax. The side lobes when the axis is short unite be- hind it. In the typical species they are divided by a furrow, which often becomes obsolete. In A. hjerulji and A p)^i^nicauda Genus Agn ostics. — Vogdes. 383 an elevated ridge extends from the spines of the pygidiiim to the axis. In the section Lcevigati^ the dorsal grooves are limited on the head, only partly defining the glabella; they are also limited on the pygidium, especially in rear, as in A. Icevigatus Dalm. , plate X, fig 3. In the section Arthrorhachis the glabella is prominent, long and marked with small basal lobes; the axis of the pygidium is short, as in Agnostus tardus Barr. PART 3. DESCRIPTION OF THE NORTH AMERICAN SPECIES. The insignificant genus Agnostus surpasses in number of spe- cies all the other genera of the order Trilobita; in the primordial fauna we have a total number of ninety species, excluding the Varieties. The species range from the Olenellus zone to the Lower Silurian. The zone with Paradoxides contains 44 species and several varieties; the Olenus is not so well represented: but, the genus outlived both these genera and extends into the Cera- topyge chalk (.4. sideadladhi) also in the Orthoceras zone {A. lentiformis &c). The genus dies out in the zone with Asaphus and Trinucleus (^4. trinodus &c). In North America the genus is represented by twenty-eight species which may be arranged into the following zones and sections: OLENELLUS ZONE. Agnostus nobilis Ford, 1872. This is a doubtful species and may belong to the genus Micro- discus. Section I, PARVIFRONTES.— The glabella is only partly de- veloped in this section {Agnostus hrevi/rons Aug., plate X, fig. 12). Agnostus desideratus Walcott, 1890. Plate X, fig. 7. Cf. Agnostus jn-olongus Hall. Diagnosis. Head about as broad as long, broadl}' rounded in front, sides curving in slightly towards the posterior margin, which slopes obliquely inwards from the posterolateral angles to the glabella. The glabella is less than f the length of the head. A narrow raised rim extends all around the margins, ex- cept across the base of the glabella, which is subcylindrical, nar- row, with a small node on the posterior third of its medium line. Surface smooth. Locality, Salem, N. Y. This species is of the 384 The American Geologist. June, i892 type A. pan- if mm Linrs. which appears with the genus Fara- doxidea in Norway. The pygidium of A. jrroJongus Hall, pi. x, fig. 10, has a similar form to the head of this species. The author illustrates only the head. An associated pygidium has a prominent axis bordered by a narrow convex space between it and the limb. The axis does not exhibit lateral, or transverse furrow. An elongated median tubercle is the only ornament. PARADOXIDES ZONE. Section II, LONGIFRONTES- This section is distinguished by its strongly projecting glabella and axis, which latter is generally moderately long. Crust smooth. The cheeks grooved. The crust on the cheeks and pygidium is provided with raised points. Limb generally narrow. The cheeks in front of the glabella and side lobes of the pygidium, behind the axis, divided by a groove. {Agnostus imnctnosuH Kng., pi. IX, fig, 2, also yl. pUiformis pi. IX, fig. 14). Agnostus acutilobus Matthew, 1885. Plate ix, fig. 1. I)iag)iosis. — Body elliptical, elongated. Head semi-elliptical. Dorsal furrow faint, marginal furrow and fold sharply defined. Glabella subconical, length f of that of the head. The glabella is divided into two lobes ; the anterior lobe is ^ of the length and subtriangular, posterior lobe extends to the base of the head. It has an elongated ridge on the anterior half, with two faintly marked lateral furrows on the lateral edges of this lobe. The basal lobes are divided off by a sigmoid farrow and depressed below the level of the glabella. Occipital ring narrow. The cheeks are somewhat full especially in front and divided by a furrow, each cheek is seamed across by a faint furrow. Thorax of two segments ; the first has five lobes, the second onl}^ three. Pygidium subelliptical. Axis is oblanceolate, nearl}' ^ as wide as the pygidium and its length is about f of that of the pygi- dium, narrowed in the anterior third, and crossed in that part by two transverse furrows; the included lobe bears an elongated tubercle ; lateral lobes of the p3^gidium moderately elevated and united behind the axis. Surface smooth externally, but it is granulated on the inner surface of test. Locality. St. John group, Porter's brook, St. Martin's. Genus Agnostus. — Yogdes. 385 The species differs in minor points from A. gihhus var. hyhridus Brog- ger, especially in having an elongated ridge on the front of the posterior lobe of the glabella. Agnostus obtusilobus Matthew, 1885. Plate ix, fig. 3. Cf. A. scarceoides Salter, 1872, from which it differs by a nar- rower glabella with a more obtuse frout. Diagnosis. — The head of this species is like that of A. acuti- loha Matthew. The pygidium described under this name is sub- quadrate in form, wider behind than before, and has a pair of spines at the outer angles. The axis is nearly one-half as wide as the pygidium, about four-fifths of its length and projects for- ward beyond the side lobes ; it is obtusely lanceolate, somewhat narrowed in the middle, and divided into three lobes, of which the posterior is a ^ longer than the length of the two anterior. The middle lobe is elevated in the middle, and bears an elongated tubercle on the axial line; there is also a faint tubercular eleva- tion on the middle of the anterior lobe. The lateral lobes of the pygidium are somewhat narrowed in the middle of their length by - the projecting sides of the axial lobe, and rapidly behind the pygidium, where they connect. The dorsal furrow is deepl}" im- pressed all around, and at the posterior angle is ver}' close to the marginal furrow; this furrow is angled forward to the axial lobe and quadrately rounded at the posterior side of the pygidium. Locality. St. John group, Porter's and Hanford brooks, St. Martin's. Agnostus tessella Matthew, 1885. Plate ix, fig. 4. Diagnosis. — Head semi-elliptical, higher in the middle and rear part. Dorsal furrow distinct on the posterior f of the gla- bella, faint on the other ^. Limb strongly elevated ; the interior groove deep and strongly impressed. Griabella cylindro-conical, rounded in front, the width ^ of that of the head; the length five- sevenths. The frontal lobe of the glabella is depressed to the level of the cheeks, and almost obsolete; the posterior lobe is cylindrical, rounded behind, bounded in front by a straight, deep furrow, and bears a small tubercle ^ from the front. Basal lobes small. ' Thorax of two segments. The anterior segment bears five lobes of which the two lateral pairs are globose; the axis is transversely elongated, wider behind than before, and bears a minute tubercle at the axial line. The posterior segment is simi- 386 The American Geologist. . June, i892 lar except the tubercle. The pygidium is semi-elliptical, some- what wider than long, strongly elevated along the axis, trun- cated in front at the lateral thirds. The axis is cylindro-conical, width ^ the pygidium, length f; it bears an elongated tubercle on the axial line at the anterior \ ; short furrows indent the sides of the axis, opposite the ends of this tubercle. The side lobes are narrow and divided at the extremity of the axis by a furrow, connecting the dorsal and marginal furrows. Lomlity. St. John group, at Porter's brook, St. Martin's. \gnostus acadicus Hartt, 1878. Plate ix, fig. 7. Syn. Aguostus similis Hartt. Diagnosis. — Head convex, depressed. Limb narrow, slightly elevated. Glabella slightly less than f of the length of the liead^ long, elliptical, depressed convex, but more elevated than the other parts of the head ; frontal lobe of the glabella, sub-circular and occupying about ^ of the glabella; basal lobes small, but distinct. Cheeks of the same width throughout and united in front of the glabella; they are convex, more elevated along their inner margins, but sloping outwards roundly and evenly. The genial zone has a narrow, shallow, flat space or groove which fol- lows the limb; on going posteriorly along the lateral margins it loses gradually its width towards the posterior angles of the head. Thorax unknown. Pygidium similar to the head. The limb slightly raised, separ- ated from the sides by a shallow but well marked groove running parallel to the margin. This groove widens at the point where it bends to go forward along the sides, in such a way as to en- croach on the thin out of the limb; just before reaching the an- terior margin it narrows itself from the inner side, so as to cause the side lobes to widen somewhat anteriorly. These are narrow, flattened, about ^ as wide as the axis, narrowing to a point just behind the axis where they do not unite. The axis is about five-sixths of the length of the p3'gidium, lan- ceolated, flattened, more elevated than the side lobes of the P3'gi- dium. Dorsal furrows distinct. The axis has a small tubercle located on the median line about ^ its length from the front mar- gin. Surface smooth. Locality. St. John group, Saiat John, N. B. The head of this species approaches that of A.neon, Hall & Whitfield. The A31ERICAN Geologist. Vol. IX, Plate X. NORTH AMERICAN SPECIES OF AGNOSTUS. {•OlSlTttSllYl Z4l Genus Agnostics. — Vogdes. 387 Agnostus acadicus var. declivis Matthew, 1885. ,P1. ix, fig. 8. The author compares this species with A. secretus Walcott. Agnostus regulus Matthew, 1885. Plate x, fig. 11. Diagnosis. — Head elongate, semi-elliptical, with straight sides^ posterior contour .broken by the projecting glabella, and narrow occipital ring. Dorsal furrow distinct, marginal furrow and limb sharply defined; the latter diminishes towards the posterior angles of the head. Glabella large, consisting of two lobes; the anterior lobe semi-circular, wider than the posterior lobe, elevated above the general contour of the surface and undulate with broad furrows, radiating from the back of the lobe; posterior lobe flattened, cylindrical, with a faint broad median transverse furrow interrupted at the summit of the glabella by a node, elongated on the line of the axis. The cheeks are narrowed in the middle, there being a crescent-shaped limb in front of the anterior lobe of the glabella, and an expanding cheek on each side of the posterior lobe of the glabella. The pygidium is elliptical. The axial lobe large, high, obtusely Clavate, constricted in the centre and divided into three lobes; the middle lobe is larger than the combined length of the other lobes, and has a median ridge-like tubercle. This lobe is indented in the middle of its length on each side by a short furrow ; the an- terior lobe is narrow and ring-like; the posterior lobe is sub- lunate. Limb distinct. The side lobes of the pygidium narrow in rear to conform with the axis. Locality. St. John group, at Portland, Hanford and Porter's brook, St. Martin's. This species is of the type A. rex Barr. Section PARVIFRONTES. Agnostus umbo Matthew, 1885. Plate x, fig. 9. Diagno.ns. — Head broadly transversely elliptical, high and contracted behind, sloping from the glabella in all directions. Marginal fold and furrow strongly marked. Dorsal grooves dis- tinct. Glabella suborbicular, rounded in front, and behind bearing a small tubercle on the axial line, ^ from the front. Length of the glabella ^ that of the head. Pygidium semi-ellip- tical. Dorsal and marginal furrows deeply impressed; axis coni- cal and greatly elevated above the rest of the pygidium; it bears a small tubercle ^ from the front. The limb is rather wide at ^P^ OP thb'^C^ 388 The American Geologist. June, i892 the extremity, of the pygidium, and is rounded at the anterior corners. Locality. St. John group, at Porter's brook. This species is of the type A, %)ctrvifrons Linrs. Section III, LIMBATI. (xeneral form subquadrate, head has a broad limb, basal lobes large. The cheeks in front of the glabella are not divided by a central groove or grooved at the sides. The p3'gidium is usually produced into lateral spines. {Agnostus rex Barr, pi. x fig. 13). Series A. (REGII). Distinguished by its broad limb, dimin- ishing cheeks and side lobes of the pygidium. Both the anterior lobe of the glabella and the posterior lobe of the pygidium ex- pand. (Type Agnostus rex Barr). Series B. (FALLACES). This series has a smaller head, and moderately broad limb. Cheeks large; basal lobes rather large with a broad posterior lobe to the axis of the pygidium. (Type Agnostus f alia X Linrs, pi. x, fig. 2). Agnostus vir Matthew, 1885. Pi. x, flg. 14. Diagnosis. — Head elongate, semi-elliptical, with straight sides and angulated behind. Dorsal furrow distinct. Marginal fold and groove rather flat and broad. G-labella subconical, obtuse in front, expanded ])ehind. Length about five-sevenths of that of the head. The anterior lobe of the glabella is about two-fifths of its length; it is elliptically rounded in front, and obtusely behind; the posterior lobe is narrowed behind, and in that part is decidedly elevated above the rest of the head; a sigmoid furrow cuts ofl[' a depressed basal lobe on each side. The cheeks are moderateh' elevated, and of equal width all around the glabella. The thorax consists of two segments, the first is divided into three lobes of which the outer pair is globose, the axis is elon- gated, transverse and indented on the front side by two strong furrows extending ^ wa}^ across ; the second segment is similar to the first, except that there are no grooves on the axis. The pygidium is subquadrate, and armed with two lateral spines: its width one-fifth greater than its length. Axis cylin- dro-conical, obtusely pointed behind, and bears an elongated tu])ercle pointed backwards. The side lobes of the pygidium are about ^ the width of the axis and narrowed towards the posterior end of the pygidium, where they connect. The marginal furrow Genus Agnostus. — Vogdes. . 389 increases in width going backwards as far as the posterior lateral angles, where it is as wide as the lateral lobe of the p3'gidium, but harrows again towards the extremity of the pygidiuni. The limb increases in width from the front as far as the lateral spines, behind which it is constricted; at the anterior end it is angulated towards the axis, in the rear third broadlj^ rounded. Locality. 8t. John group, Portland and at Hanford brook, St. Mar- tin's. The species differs but slightly from Agnostus fallax YSiT.ferox Tullb. from the Scandinavian formation at Andrarum with Paradoxides tessini. Agnostus vir var. concmnus Matthew, 1885. Plate ix, fig. 13. This variety varies but slightly from Agnostus vir. DIKELOCEPHALUS ZONE. Section LONGIFRONTES. Agnostus americanus Billings, 1860. Syn. Agnostus richmondensis Walcott. Plate ix, figs. 5 and 11. Diagnosis. — Head oblong, semi-oval, rather strongl}" convex, most elevated at the posterior quarter of the length, thence de- scending with a depressed convex slope in all directions to the sides and front. Limb verj^ narrow. The glabella is elongate oval, width ^ that of the tvhole head, length rather- more than f the length of the head. It has two transverse furrows which completely or partially divide it into three lobes. The anterior fur- row extends all across at ^ or a little more of the length from the front. The posterior furrow is interrupted in the middle, and is only distinctly seen on each side, penetrating ^ the width, while its position is a little in advance of the posterior third of the length of the glabella. The space between the two inner extrem- ities of the posterior furrows is occupied by a low conical tuber- cle, with the apex directed backwards. Basal lobes small and triangular. Dorsal groove distinct. Cheeks divided in front of the glabella by a furrow. The surface is ornamented by from 15 to 20 irregular, slightly impressed radiating rugose stride. The pygidium is striated like the head. The axis has three lobes with an elongated median tubercle, extending across the anterior and middle lobes ; the posterior lobe is equal in size to the other lobes. Locality. Point Levis, Quebec. This species approaches A. trisectus Salter, which occurs at Andrarum, Sweden with the genus Peltura. 390 The American Geologist. June, 1892 Agnostus canadensis Billings, 1860. Plate ix, fig. 9. Dlag)iosis. — Head obtusely oblong, semi-oval, width a little greater than the length, a concave border nearly as wide as the glabella all around. Glabella in width less than | the width of the head, and in length a little more than | the length of the head. Basal lobes small. The transverse furrow marking the frontal lobe of the glabella is located a little in advance of the mid- length ; the tubercle is obscure and appears to be indicated by the small indentation in the middle of the transverse furrow. The cheeks are separated in front of the glabella by a furrow. The author doubtfully figures a pygidium of this species. It has a similar form to that of the head of A. canadensis with the concave border all around the margin. The axis is obtusel}^ cla- vate, and marked with two joints. The posterior joint is large and convex, extending quite to the concave border, where it is full half as wide as at the furrow which divides the two joints. The tubercle is situated in the transverse furrow and makes a small indentation in the edge of the posterior joint. Tjocality. Point Levis, Quebec. Agnostus communis Hall and Whitfield, 1877. Plate ix, fig. 15. Diagnosis. — Head subparaboloid, wider than long. Surface strongly convex. Glabella nearly equaling ^ of the width of the head ; anterior third separated from the posterior lobe by a faint, transverse furrow. Central part of the glabella ornamented bj^ an elongated and angular tubercle. Dorsal furrow distinct. Cheeks separated in front of the glabella by a groove. Basal lobes triangular. Limb flattened. Thorax unknown. The pygidium with a flattened limb, which is ornamented with lateral spines. Surface strongly convex ; in the anterior half , the dorsal furrow being directed gently inward for half their length, and then suddenly deflected outward, with a slight curvature, be- coming obsolete a little behind the middle of the length. A.n elongated angular node marks the axis near its anterior margin. Surface of the head and pygidium smooth. Locality. White Pine, Nevada. This species is of the type Agnostus cyclo'pyge Tullberg. Agnostus coloradensis Shumard, 1861. Plate ix, fig. 16. • The description was drawn from a single example found in Burnet county, Texas, near the mouth of Morgan's creek; the Genus Agtiostus. — Vogdes. 391 author states that there is no fissure extending from the glabella to the anterior margin. The absence of this groove ma}- be due to the state of preservation. This species agrees in every other re- spect with A. neon. Agnostus neon differs from A. commuma in minute points, especially in the absence of the tubercle on the glabella. Agnostus orion Billings, 1860 (cf. A. jnsiformis Linne). Plate IX, fig. 12. Diiignosia. — Length and breadth about equal, sub-circular, con- vex, a very narrow margin all around. Glabella not quite f the whole length, very convex; a transverse furrow at one-third the length from the apex ; small triangular basal lobes without a median tubercle. Cheeks divided in front of the glabella by a furrow. Locality. Point Levis, Quebec. The same term was used by Barrande in 1846 for a species of this genus. If this species differs from A. pisiformisii is only in the absence of the median tubercle, which may be due to its state of preservation. There is a slight indication of the tubercle on one of my cabinet speci- mens from Point Levis. A pygidium from the same locality is similar to that of Agnostus insiformis. Agnostus josepha Hall, 1863. Plate ix, fig. 17. Diagnosis. — Head semi-elliptical, margined by a flattened or concave narrow limb; genal angles produced into short spines. Glabella prominent, narrow, extending about f the length of the head, and crossed by a shallow furrow near the anterior end. The posterior lobe is marked by an oblique furrow on each side; a small node on the summit at the anterior termination. The trian- gular space on each side between the transverse and oblique fur- rows is like- wise elevated into a low node. The posterior central portion is gibbous. The ba?al lobes small and triangular in form. Cheeks divided in front of the glabella b)^ a furrow. Pygidium of the same form as the head. Axis prominent, subquadrate, wider than long, nearly ^ the length of the pygidium, bearing a node or short spine on its posterior extremity ; sides and body of the pygidium, outside of the axis, highly convex. Locality. Trempealeau and elsewhere on the Mississippi about lake Pepin, Wisconsin. The species occurs with Anomocare wisconsensis and Ptychaspis granulosa. 392 The American Geologist. jmie, 189^ Agnostus richmondensis Walcott, 1884. Plate ix, fig. 11. Diagnosis. — Head moderately convex, length and breadth equal. Glabella f the length and a little more than ^ as wide at the base than the width of the head; elongate, conical in outline, strongly defined by the dorsal furrows, with the anterior third separated by a distinct transverse furrow ; a little less than mid- way between this furrow and the posterior margin, a short furrow penetrates from each side towards the base of a minute tubercle situated on the median line. Basal lobes small, triangular. Cheeks more convex than the glabella, separated in front of the glabella by a furrow. Limb narrow. Surface ornamented by slightly irregular depressed lines that indent the surface from the margin nearly to the edge of the strong dorsal furrows. Surface smooth under an ordinary magnifying power. Locality. Prospect mountain, Nevada. This species is identical with Agnostus americanus Billirgs. Agnostus maladensis Meek, 1873, aff. Agnosfas joseplia. The author proposes this name for a species from Malade City, Utah, which is closely allied to Agnostus joscplxi Hall, except that the specimens do not exhibit the spines on the genal angles of the head; the author remarks "none of which are in a condition to remove all doubt on this point." Section LIMBATI. Agnostus bidens Meek. Plate x, fig. 5. Diagnosis. — Head moderately convex, slightly wider than long, bordered by a rounded margin with a strongly defined marginal groove. Glabella convex, narrow, more than | the length of the head, converging anteriorly, sub-angular in front; two oblique furrows posterior to the center enter from each side, and unite just in advance of a small node, on the center of an elevation, de- fined behind by a transverse furrow that bends backwards; be- tween this furrow and the occipital furrow a narrow band extends, widening out laterally, forming the basal lobes. Dorsal furrow distinct. Cheeks convex and sloping rapidly to the marginal groove from the somewhat elevated central portion. Thorax un- known. The pygidium is armed with lateral spines, and is strongly convex. Axis conical, extending more than f of the en- tire length, ornamented with an elongated, angular tubercle on the Ge7ius Aff7iostns. — Vogdex. 393 anterior portion, with a transverse furrow just before it, separating a narrow anterior portion; in some examples a faint transverse furrow crosses back of the tubercle. Surface of the head and pygidium finely granulose. Locality. Gallatin City, Montaaa, also in the Eureka District of Ne- vada and elsewhere. Agnostus tumidosus Hall and Whitfield, 1877. Plate x, fig 8. Diagnosis. — Head highly dome-shaped in outline, slightly con- tracted near the occipital border, very convex. Limb narrow, flattened. Dorsal furrow distinct. Glabella small, less than f as long as the head, conical and very convex, especiall}' tumid in the lower part ; the central tubercle marked near its edge by a very slight line which presents the appearance of a border surrounding it. Frontal lobe about \ of the length of the glabella. Basal lobes triangular and minute. Thorax unknown. The highl}^ dome-shaped outline with the form and markings of the glabella distinctly mark this species. Locality. Eureka, Nevada. The species is of the type A. quadratus Tullberg. Agnostus interstrictus White, 1874. Plate x, fig. 6. Diagnosis. — This species of the type A. fallax Linrs. is ellip- tical in form with a smooth surface. The head is broader than long. Limb narrow, forming a narrow linear depression between it and that portion of the head which it incloses. Glabella bilobed, conical, well defined by the dorsal furrows, and sharply rounded in front. A minute tubercle on the median line; near the poster- ior end; the frontal lobe is marked off by a shallow transverse furrow. Thorax of two joints, narrower than the head and P3'gidium, giving the body the appearance of being constricted at the middle. Axis broad, both its joints tumid at the ends, where they reach the dorsal furrows; lateral lobes very narrow, pleurae about as wide as long, each pleurae tumid and rounded at the ex- tremities. Pygidium in form like the head. Axis a little longer than the glabella, moderately convex, with a minute tubercle on the median line near the anterior end. Sides between the mar- ginal furrow and axis convex. The lateral angles of the pygid- ium are produced into sharp spines. The basal lobes of the gla- bella are very minute. Locality. Antelope Springs, Utah. 394 The American Geologist. june, 1892 Section L^VIGATI. The dorsal grooves marking the glabella and axis of the thorax and pygidium, are wanting or faintly indi- cated. Crust smooth, sometimes with slight indications of striae. Limb on the head disappearing; on the pygidium it becomes broad. {Agnostus Icvvigatufi. Dalm., plate X, fig. 8). Agnostus disparilis Hall, 1863. Plate x, fig. 15. Diagnosis. — Head semi-elliptical, convex towards the posterior side, and abruptly sloping in front; length and breadth nearly as 3 to 4, a little concave on the posterior margin and marked near the edge by a narrow groove on each side of the middle; the centre slightly elevated close to the margin. The limb is a little wider in front than at the sides. The pygidium (?) is a little wider than long. The trilobation extends nearly to the posterior extremit}^, and is separated from it only by a narrow border. The axis is fully once and a half as wide as the side lobes, somewhat flattened on the summit, and very distinctly limited by the dorsal furrows. The pygidium figured with this species ma}' be that of the genus Microdiscus. Locality. Oseola Mills, on tlie St, Croix river, Wisconsin. Agnostus parilis Hall, 1863. Plate x, fig. 4. Diagnosis. — Head semi-elliptical; length and breadth about equal, very convex in the posterior part, and curving downwards to the anterior margin. The central portion of the posterior part is limited by a faint curving groove; and anterior to its limits there is a slight elevation, which may have a node on the surface of the crust. The posterior margin, just within the angles, is pro- duced in a minute node. The limb gradually expands from the posterior angles to the front, where it becomes well defined. The pygidium is slightly truncated at the anterior angles, the marginal rim narrower towards the articulating border. The central part is slightly more elevated and limited by furrows diverging from the anterior margin. On the median line, at a point ^ the length from the front margin, there is a distinct elongated tubercle. Locality. Shores of lake Pepin. Agnostus prolongus Hall and Whitfield, 1877. Plate x, fig. 10. Diagnosis. — Head elongated, or very high dome-shaped in out- line. Surface depressed, convex in front and gradually rising to near the occipital border, where it becomes low, tumid. Glabella Genus Ag7iost us. — Vogdes. 395 very indistinct, of conical form, with triangular basal lobes. Limb narrow, somewhat rounded, gradually fading out along the postero- lateral angles. Pygidium (?) much like the head, but much shorter in proportion to its width. The axis occupies more than ^ of the width, short and rounded, obconical, ornamented by a node in its upper end, and divided across by a doubly curved transverse fur- row near the lower end. Dorsal furrows distinct. Limb flattened. Locality. Eureka, Nevada. Section FALLACES. Agnostus seclusus Walcott, 1884. Plate x, fig. 16. Diagnosis. — Head strongly convex, a little longer than wide^ with a slight contraction posteriorly. Limb narrow with a distinct groove between it and the cheeks. Dorsal furrows well defined. Basal lobes distinct. Glabella about half the length of the head, strongly convex and squarely truncated in front; at about the an- terior third a broad, short furrow penetrates on each side a Short distance, and posteriorly a rounded node is separated from each lateral angle by slight furrows, forming the basal lobes. The cheeks slope rapidly towards the marginal groove, on the sides and more gradually to the front. Surface finely granulose. Locality. Secret Canon shales, Eun^ka District, Nevada. ASAPHUS ZONE. Section IV, ARTHRORHACHIS, type Agnostus tardus Barr. Agnostus galea Billings, 1865. Plate ix, fig. 6. The author describes in The Palaeozoic Fossils of Canada, Vol. 1, 1865, p. 291, Agnostus gajlm and A. fahius from Table Head and Pistolet bay, Newfoundland. Both these species are of Lower Siluric types, the first of Agnostus tardus Barr, and the second of A. lentifonnis Ang. The species appear with the gen- era Asajihus, lUeenus and Triarthrus Jischeri., etc. Diagnosis. — Head strongly convex. Limb narrow. Glabella convex, strongly elevated above the general surface, occupying . about f of the whole length of the head. Smooth, no tubercle, but with slight indentations on each side, at about the mid-length. Dorsal furrows distinct. Basal lobes triangular. Pygidium in contour and convexity, like the head. Axis strongly convex, well defined all round by the dorsal furrows; a furrow runs all across at ^ the length from the apex ; a short one on each side at f the 396 The Arnerican Geologist. June, i892 length from the apex. The tubercle forms a longitudinal medium lobe in the anterior | of the axis. The tubercle is at the anterior margin, slightly elevated above the general convexit}" of the axis, it is less elevated just over the anterior pair of furrows, but behind this point it rises to twice the hight and terminates abruptly at the posterior furrow. The anterior lobes of the axis are dis- tinctly separated from the tubercle b}^ a narrow groove; the second two are not. Surface apparently smooth, but with indi- <3ations of small wrinkles which unite with each other, so as to give a reticulated aspect, similar to that of A. reticulatus Ang. The species differs from A. tardus Barr, in having a shorter axis in the pygidium, and in having the node of uniform hight its whole length. Agnostus fabius Billings, 1865. Plate ix, fig. 10. Diagnosis. — Head semi-elliptical, uniformly and moderately convex. Liml) very narrow. Grlabella scarcely elevated above the general surface, not defined in front; obscurely so in the posterior half by the dorsal furrows, which are parallel, and disappear about the middle of the head. Basal lobes small, triangular. Pygidium slightly more elongated than the head. Limb narrow, flat. Axis about ^ the whole width; it has two pairs of transverse furrows, the posterior reaching the median line, where there is a small rounded tu})ercle, located slightly behind the mid-length of the axis. The anterior furrows are half way between the tuber- cle and the front margin, their inner extremities separated by about one-third the width of the axis.