young shells the volutions are closely coiled, as shown in figure 2 of plate 15. In the casts of older specimens the apex is decollated and the termination smoothly rounded, as if separated by a septum, no evidence of a continuation above being perceptible. Figures 3, 4 and 5, of plate 15, represent this feature. The interior volutions being rounded, the angularity on the upper side is scarcely perceptible before the end of the second volution, and that of the lower side about the same time or a little later. In some of the casts of the interior there is a low, undefined angularity upon the back of the shell, as shown in fig. 6 of plate 15. This species appears to be very nearly identical with Euomphalus Wahlenbergii of GOLDFUSS (Petrefacta, vol. 3, page 82, plate 189, figs. 7 a, b), from the Eifel. That species also presents the same features in the decollation of the earlier volutions, and the rounded apicial extremity, as shown in figures 3, 4 and 5 of plate 15. The European form is associated with E. planorbis, a species much resembling E. clymenioides, which occurs in the same beds with E. Decewi in western localities, and with other forms similar to those of New York. The specimens of this species retaining the shell, figured in the Geological Survey of Ohio (Vol. I, plates 19 and 20), reveal characters of the surface not shown in the New York and Canadian specimens. A single remarkable specimen, communicated by Dr. C. ROMINGER, preserves still other features not illustrated in the Ohio specimens. (See plate 27 and supplementary notice of the species.) Formation and localities. In limestone of the Upper Helderberg group, at Stafford, Batavia, and other places in Western New York; a single specimen of the species has been found at Schoharie. in the same limestone near Cayuga, Ontario. EUOMPHALUS TIOGA. It is of common occurrence PLATE XV, FIGS. 9, 10, AND PLATE XXVII. Euomphalus Tioga, HALL. Illustrations of Devonian Fossils: Gasteropoda, pl. 15. 1876. SHELL discoid; upper side moderately concave from the dorso-lateral angle; lower side broadly umbilicate, the dorso-basal margin acutely angular. Periphery flattened, oblique to the plane of the shell, and sloping outwards from the upper margin. Volutions probably three or more, gradually enlarging from the apex; the remains of two only are shown in the specimen figured, in which the extremity of the outer volution is much wider than high. Aperture unknown; transverse section triangular, with the inner angle truncated. SURFACE of the upper side and periphery preserving the remains of striæ, which bend abruptly backwards at the lower carina. The specimen is essentially a cast of the interior, and somewhat worn. The species is extremely similar to the E. Decewi, with more slender volutions, and the dorso-basal margin more acutely angular. Formation and locality. In the upper part of the Chemung group in the town of Nichols, Tioga county, N. Y. EUOMPHALUS PLANODISCUS. PLATE XVI, FIGS. 1-4. Euomphalus planodiscus, HALL. Thirteenth Rep. N. Y. State Cab. Nat. Hist., p. 109. 1860. 66 66 66 SHELL discoid planorbicular; spire depressed, the apex being below the plane of the outer volution; lower side broadly concave; periphery rounded. Volutions about four or five, slender, barely contiguous, very gradually enlarging from the apex, and regularly rounded, the adjacent sides not being perceptibly flattened; the last one near the aperture somewhat flattened above. Aperture slightly expanded, subcircular, a little transverse. SURFACE marked by fine close striæ, which are sometimes crowded in regular fascicles, giving the appearance of annular ridges, which bend a little forward at the edge of the periphery. This species presents few strong features of distinction; but the surface markings, when preserved, seem to be sufficiently characteristic. Formation and localities. In the Goniatite limestone of the Marcellus shale (Hamilton group), at Manlius, and other places in Western New York. ECOMPHALUS (STRAPAROLLUS) INOPS. PLATE XVI, FIG. 5. Enomphalus inops, HALL. Illustrations of Devonian Fossils: Gasteropoda, pl. 16. 1876. SHELL discoid; spire depressed-convex, the apex slightly elevated above the plane of the outer volution; lower side broadly and deeply concave. Volutions three or more, curving gently inwards from the periphery, without angularity at the dorso-basal margin. Upper side of volutions convex, the last one rounded; a transverse section near the aperture distinctly broad oval, with the lower side making a longer curve than the upper. SURFACE Concentrically striated. This species is known at present in a single specimen which differs sufficiently from all the others in the New York rocks to be readily distinguished by the peculiar concavity of the umbilical area. In general aspect this form resembles the young of E. Decewi, but the volutions increase in size less rapidly, the umbilical depression is comparatively deeper, and there is no evidence of angularity of the outer volution. Compared with E. Hecale of the Chemung group, the lower side of the volution is more abruptly curving into the umbilicus, and not flattened as in that species (fig. 10, plate 16). Formation and locality. In the Schoharie grit, at Schoharie, N. Y. EUOMPHALUS (STRAPAROLLUS) RUDIS. PLATE XVI, FIGS. 6, 7. Enomphalus rudis, HALL. Illustrations of Devonian Fossils: Gasteropoda, pl. 16, figs. 6,7. 1876. SHELL discoid. Volutions about four when entire, rounded above and slightly less convex below, curving abruptly from the inner side into the broad umbilicus; periphery rounded; section near the aperture broadly oval; inner volutions rising above the plane of the outer one. SURFACE marked by fine striæ of growth, which are often irregular and crowded in fascicles, and sometimes become sharply defined towards the aperture. The specimens of this species are imperfect, and the entire characters cannot be determined. The inner volutions are moderately elevated above the plane of the outer one, differing in this respect from E. inops, while the abrupt depression of the umbilicus from the inner margin of the volution is a distinctive feature. The spire is a little more elevated than that of E. Hecale, and the base of the outer volution is rounded and not flattened as in that species. It differs very little from entire specimens of E. Eboracensis, except in the contact of its volutions. Formation and locality. In the shales of the Hamilton group, at West Bloomfield, Ontario county, N. Y. EUOMPHALUS (STRAPAROLLUS) HECALE. PLATE XVI, FIGS. 10-14. Euomphalus Hecale, HALL. Illustrations of Devonian Fossils: Gasteropoda, pl. 16, figs. 10-14. 1876. Compare Euomphalus depressus,* HALL (non Gold.). Geol. N. Y. Surv. Fourth Geolog. Dist., p. 291. 1843. SHELL discoid, spire depressed. Volutions about three or four, contiguous, rounded, the inner ones slightly elevated above the plane of the outer one, gradually enlarging from the apex, very slightly expanding at the aperture and flattened on the lower side. Umbilicus broad, descending abruptly from the inner basal margin of the volution, which is rounded on that side. SURFACE Concentrically striated-the striæ often crowded in fascicles or ridges towards the aperture. This is probably the same species described in the Report of the Fourth Geological District as Euomphalus depressus (not E. depressus of Goldfuss).* Comparatively few specimens of this form have occurred among large collections of other fossils from the same formation, and these are principally casts of the interior, which sometimes preserve marks of the external striæ, and ridges left by the stronger fascicles, near the aperture. In form and proportions it resembles E. laxus of the Hamilton group, from which it differs in having the volutions in contact. Formation and localities. In the Chemung group at Rockville, Allegany county, near Ithaca and Elmira, N. Y., and at Meadville, Penna. * The original of E. depressus, HALL, is not now accessible to the author for comparison. EUOMPHALUS (PHANEROTINUS) LAXUS. PLATE XVI, FIGS. 8, 9, 16-18. Enomphalus lacus, HALL. Descriptions of New Species of Fossils, etc., p. 26. 1861. SHELL discoid; lower side broadly umbilicate. Volutions about four, nearly in the same plane, the inner ones rising moderately above the plane of the outer one, disjoined throughout their entire extent, very gradually and regularly expanding from the apex; section circular. Aperture (so far as known) subeircular, scarcely expanded. SURFACE marked by crowded concentric striæ, which are sometimes regular and equal, and on some parts of the shell more closely arranged, and all directed a little forward, from the inner side of the volution. The greatest diameter of the largest specimen seen, is one inch and fiveeighths; the prevailing forms have a diameter of about one inch, while many are of smaller size. This species differs from any other in this series of strata, except the following one, in the distinct separation of the volutions throughout their entire extent. The impressions in stone are strongly marked by the transverse striæ, which are often crowded in fascicles, and the casts preserve fainter impressions of the same markings. Recent examinations of the specimens illustrated (ut. cit.) as Ecculiomphelus comes have satisfied me that they are imperfect conditions of E. larus, having all the external characters of that species except the inner volutions, which have been decollated or removed during the maceration of the shells. I therefore propose to unite these two imperfect forms, figs, 8 and 9, with the typical forms of the species, figs. 17 and 18. The Partius paradacas (plate 16, fig. 16), described by Prof. WINCHELL, from the Burlington sandstone of Iowa, is an extremely similar form with Ecs. The perceptible difference, on comparing casts of that species, is a |