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GASTEROPODA, PTEROPODA AND CEPHALOPODA

OF THE

UPPER HELDERBERG, HAMILTON, PORTAGE AND CHEMUNG GROUPS.

GASTEROPODA.

PLATYCERAS, CONRad.

PLATYCERAS (ORTHONYCHIA) SUBRECTUM.

PLATE I, FIGS. 1, 2.

Orthonychia HALL. Geology of N. Y. Surv. Fourth Geolog. Dist., p. 172, f. 3. 1843.
Platyceras subrectum HALL. Twelfth Rep.
Platyceras (Orthonychia) subrectum HALL.

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N. Y. State Cab. Nat. Hist., p. 18, fig. 1859.
Descriptions of New Species of Fossils, etc., p. 1.

1861.* Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 29. 1862. Illustrations of Devonian Fossils: Gasteropoda, pl. 1. 1876.

SHELL unguiform, elongate, subspiral, making not more than a quarter of a volution in the length of three-fourths of an inch, below which it is entirely straight. Apex minute, abruptly incurved, solid, nearly cylindrical, for a short distance below the apex, and gradually compressed, becoming a little concave on the posterior side. Aperture somewhat oblique.

SURFACE marked by concentric striæ, which are sometimes crowded together, forming ridges or wrinkles.

* Contributions to Palæontology. Continuation of Appendix C [of the 14th Rep. State Cab. Nat. Hist., published July, 1861]. Descriptions of New Species of Fossils, from the Upper Helderberg, Hamilton and Chemung Groups, Albany, 1861. Pages 1-24 of this paper were printed and distributed in August, 1861, and the remaining portion, pp. 25-84, in September, 1861, according to the imprint at the bottom of each page. It is included in the Fifteenth Report on the State Cabinet of Natural History (pp. 26-112) together with illustrations of species therein described (on Plates 4-10) and accompanying explanations of figures.

PALEONTOLOGY OF NEW YORK.

This species is more robust and rapidly expanding than the P. dentalium, and is more enrolled at the apex; but it does not show the longitudinal sulci and ridges which are characteristic of that species.

This is the species figured in the Report of the Fourth Geological District, and the typical form for which the generic name ORTHONYCHIA was proposed. The apex or nucleus of this and of other species is usually solid, and when the shell is removed, the casts show a rounded obtuse apex, which is sometimes scarcely incurved.

Formation and locality. In the limestone of the Upper Helderberg group, near Buffalo and Williamsville, N. Y.

PLATYCERAS (ORTHONYCHIA) DENTALIUM.

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PLATE I, FIGS. 3-8.

Platyceras (Orthonychia) dentalium HALL. Descriptions of New Species of Fossils, etc., p. 1. 1861.
Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 29. 1862.
Illustrations of Devonian Fossils: Gasteropoda, pl. 1. 1876.

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SHELL slender, elongate, subspiral, making about half of one volution in the length of one inch and a half, somewhat flattened obliquely from the base to near the apex; section subelliptical, with the diameters about as two to three. The middle of the flattened sides is often a little concave, rounded towards the apex, which is minute and abruptly incurved. SURFACE marked by transverse or concentric striæ of growth, and by longitudinal sulci, which are conspicuous on the lower part of the shell, and give to the transverse striæ a strongly undulated character. Aperture oblique.

In a specimen of one inch and a half in length, the greatest diameter is less than half an inch.

This species is much more slender and less distinctly spiral than the P. tortuosum of the Oriskany sandstone, and in the same features differs in a greater degree from any of the species known in the Lower Helderberg group. Formation and localities. In the limestone of the Upper Helderberg group, near Williamsville and Buffalo, N. Y.

QIVÁLÓRD TIBKVBA

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PLATYCERAS (ORTHONY CHIA) CONCAVUM.

PLATE I, FIGS. 9-12.

Platyceras (Orthonychia) concavum HALL. Descriptions of New Species of Fossils, etc., p. 2. 1861. Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 30. 1862. Illustrations of Devonian Fossils: Gasteropoda. pl. 1. 1876.

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SHELL robust, subspiral, slender, gradually expanding above and more rapidly dilating towards the aperture, which is subquadrilateral, with the peristome strongly undulated. The specimen is imperfect at the apex, and the lower portion makes less than half a turn from the aperture in the length of about two inches; apex unknown. Anterior side of the body-volution convex and ventricose; posterior side distinctly concave; the right side moderately convex, and the left side rounded.

SURFACE marked by concentric undulating striæ.

The length of the largest fragment is about two inches; the aperture from the posterior to the anterior side is about seven-eighths of an inch, and the transverse diameter a little more than one inch.

This species resembles the P. tortuosum of the Oriskany sandstone, but is more robust and more rapidly expanding towards the aperture, which is much less oblique than in that species, while the concave posterior, and prominent anterior sides are distinguishing features. A comparison with a larger number of specimens of P. dentalium suggests that this form, in figs. 9 and 10, may be only a larger variety of that species.

Formation and locality. In the limestone of the Upper Helderberg group, Williamsville, Erie county, N. Y.

PLATYCERAS (ORTHONYCHIA) CONICUM.

PLATE I, FIGS. 13-23.

Platyceras conicum HALL. Descriptions of New Species of Fossils, etc., p. 3. 1861.

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Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 31. 1862.

Illustrations of Devonian Fossils: Gasteropoda, plates 1 and 2. 1876. SHELL erect, conical, the minute apex closely incurved. Body-volution entirely straight, with broad undefined longitudinal ridges and depressions, which become more distinct towards the aperture; height of the shell a little greater than the width of aperture, which is a little longer than wide.

SURFACE marked by concentric undulating striæ, which become sublamellose towards the aperture, and are sometimes closely crowded and wrinkled with numerous knots or nodes. Peristome deeply sinuous; the width from the anterior to the posterior side a little greater than the transverse diameter. The length of the shell is one inch and a half or more, with the aperture a little less.

This species approaches the P. pyramidatum of the Lower Helderberg group, but is less elongate, the peristome is more sinuous, and the indication of longitudinal ridges and depressions is more distinct; the crowded, wrinkled and nodose striæ are likewise a distinctive feature.

Formations and localities. In the Hamilton group, Ontario county; and in the Upper Helderberg limestone, at Darien and Williamsville, N. Y.

PLATYCERAS (ORTHONYCHIA) PERPLEXUM.

PLATE II, FIGS. 1-3.

Platyceras perplexum HALL. Illustrations of Devonian Fossils: Gasteropoda, pl. 2. 1876. SHELL obliquely conical, apex minute, closely incurved, or making a part of one volution. The body-volution slightly curved, expanding gradually from above to the middle of the shell, below which it spreads more rapidly upon one side, becoming strongly plicated; the plications beginning above the middle of the shell, and sometimes at a short distance below the apex, and increasing in number and strength towards the base. Aperture subovate; peristome deeply sinuate.

SURFACE marked by close concentric striæ of growth which become lamellose,

and crowded into undulating bands crossing the radiating ridges.

This is an extremely rare form, and is quite distinct from any of the other species; although presenting in the form of the body-volution an approach to some varieties of P. Thetis, it has not the same degree of arcuation, and has never the distinctly convoluted nucleus.

This species bears some resemblance to P. perplicatum of the Lower Helderberg group; but a comparison of specimens shows them to be quite distinct. Formation and locality. In limestone of the Upper Helderberg group, in Onondaga county, N. Y. Communicated by Prof. E. A. STRONG.

Acroculia erecta HALL.

Platyceras erectum HALL.

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PLATYCERAS ERECTUM.

PLATE II, FIGS. 4-11.

Geology of N. Y. Surv. Fourth Geolog. Dist., pp. 172, 174, f. 6. 1843.
Descriptions of New Species of Fossils, etc., p. 4. 1861.

Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 32. 1862.
Illustrations of Devonian Fossils: Gasteropoda, pl. 2. 1876.

This species, originally described in the Corniferous limestone, occurs also in the Hamilton group. The spire at the apex is closely enrolled for about one volution and a half, beyond which the body-volution becomes somewhat rapidly expanded, with the aperture often spreading. The specimens are often more arcuate than the figure in the Geological Report, and the aperture oblique, with the peristome sinuate.

The surface is marked by closely arranged revolving lamellose striæ, which, upon the lower half of the body-volution, are abruptly arched along narrow bands, corresponding with former sinuosities of the aperture.

Formations and localities. In the limestone of the Upper Helderberg group, Williamsville, and near Buffalo; and in the Hamilton group at York, Moscow, Darien, and other places.

PLATYCERAS CARINATUM.

PLATE II, FIGS. 12-29.

Platyceras carinatum HALL. Descriptions of New Species of Fossils, etc., p. 5. 1861.

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Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 33. 1862.
Illustrations of Devonian Fossils: Gasteropoda, pl. 2. 1876.

SHELL obliquely subconical or subpyramidal; the nucleus or apex minute, and making from one to one and a half volutions which are vertically compressed, and below which the body-volution is abruptly expanded; the dorsum angular, or marked by an angular carina, which often becomes double in old shells, or is rounded on the summit. This angularity or carina indicates, by the direction of the striæ, the existence of a sinus in the peristome from an early period of growth; and sometimes there may have been two such sinuosities close together, giving the double carina. There is usually a depression along one or both sides of the carina, with

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