260 
PALiEONTOLOGY OF NEW-YORK. 
Fig. 8 c. The striss enlarged. 
Fig. 9 a. Cast of the ventral valve, apparently identical with the preceding, showing the mus¬ 
cular impression and the remains of the dental laminss. 
Fig. 9 b. The interior of the valve of another specimen, showing the dental laminae of the same 
form as in the preceding figure. 
Fig. 10 a. A large individual having sharp prominent striae which are dichotomous, and crossed 
by finer striae, which remain in the depressions only. 
Fig. 10 c. Several of the striae enlarged, showing the concentric striae. 
Fig. 10 b. Cardinal view of another similar specimen, showing the narrow extended area and 
foramen. 
This shell has the character of an Orthis in many respects. The valves are almost equally 
convex, one being usually quite flat, except near the beak 5 while the other is plano-convex at 
the beak, and slightly convex below. I have united the forms given above, believing them to 
belong to the same variable species, the different appearances being often caused by partial 
exfoliation of the shell. 
Position and locality . This species occurs in the shale at Lockport, the most perfect speci¬ 
mens being found adhering to the thin calcareous layers. In other localities this shell is less 
conspicuous, though occurring at Rochester and Wolcott, and probably at intermediate places. 
621. 4. SPIRIFER BILOBUS (Linne). 
Pl. LIV. Pig. la-k. 
Anomia. Linne, Syst. p. 1154. 
Terebratula sinuata. Soweeby in Linn. Transactions, Yol. xii, p. 516, t. 28, f. 5 and 6. 
Terebratula cardiospermiformis. Hisinger, Acta. Soc. Holmiensis, Yol. iv, p. 18, pl. 7, f. 6. 
JDelthyrisl — Damah, Vet Acad. Handl. 1827, pag. 124, tab. iii, fig. 7. 
— — Hisinger, Petref. Suecica, 1887, p. 74, t. 21, f. 9. 
Spirifer cardiospermiformis. Von Buch, Sur les Spirifer et Orthis, T. 1, f. 7. 
—• sinuatus. Soweeby in Murchison’s Sil. System, 1839, pag. 630, pl. 13, fig. 10. 
JOelthyris sinuatus. Hale, Geol. Rep. 4th Dist. N. York, 1843, pag. 105, fig. 8. 
Shell bilobate, obcordate, sinuate in front; extremities of the cardinal line auriculate ; dorsal 
valve very convex, arcuate ; ventral valve flat or slightly concave (rarely a little convex) ; area 
comparatively large, triangular, with a distinct triangular foramen; surface striated; striae 
dichotomous or in fascicles, radiating from the apex to each lobe of the shell; concentrically 
marked by fine striae, which are deeply arched or sinuate in the sinus of each valve ; hinge-line 
of ventral valve marked on its inner margin by three simple teeth. 
This peculiar little species is readily distinguished from any other known, except a closely 
allied form in the Delthyris shaly limestone. Our species is evidently identical with the 
European one, as proved by a comparison with Swedish specimens, and the figures in the 
Silurian System cited above. The species of the shaly limestone of New-York attains a larger 
