280 



PALEONTOLOGY OF NEW-YORK. 



except that a greater number of plications are represented in the figure than our shell possesses. 

 A comparison with vSwcdish specimens of T. plicalella shows no appreciable dilTerence, except 

 such as might be expected from the different conditions of preservation of the shell, and the 

 material in which it is imbedded. This species is comparatively rare in our strata, though 

 abundant in strata of the same age in Gothland, and other localities in Sweden. 



Fig. 3 a, h. Ventral and dorsal view of this species. 

 Fig. 3 c. Cardinal view of the same. 

 Fig. 3 d. Profile view. 



Fig. 3 c. Several of the plications enlarged, showing the concentric striae. 



Fig. 4 a, h. Dorsal and profile views of a larger specimen, showing a greater number of plica- 

 tions than the specimens fig. 3. This is probably only a variety of the same species. 



Position and locality. In the shale of the Niagara group at Wolcott. 



642. 56. ATRYPA APRINIS. 



Pl. LVII. Fig.7a-g. 



Terthralula apriiiis. Be Veuneuii,, Geol. Russia and the Ural Mountains, Vol. 2, pag. 1)0, pl. 

 X, fig. 10. 



Shell small, roundish oval, scarcely longer than wide ; valves almost equally convex ; margin 

 not sinuate ; surface marked by 24 or 28 simple rounded plications, which are crossed by fine 

 elevated stria;, and near the base by imbricating lines of growth ; beak of dorsal valve extended 

 and incurved, and vertically truncated by a roundish foramen ; central longitudinal line of the 

 ventral valve marked by a wider space between the plications, and the dorsal valve by a small 

 plication in the centre. 



This species bears a very close resemblance to the figure of T. aprinis cited, and the 

 description corresponds so closely that it seems unnecessary to regard it as a distinct species. 

 It is an extremely neat and pretty little shell ; the only one in this group of strata, where the 

 apex of the dorsal valve is positively perforated by a round aperture for the passage of the 

 peduncle of attachment, as in the Terebratulee of modern geological periods. It is exceedingly 

 rare, but a single perfect specimen having been seen, and a second imperfect one ; showing 

 that its proportion to the immber of individuals of other species of this family is not one in 

 fifty thousand. 



Fig. 7 a, b. Ventral and dorsal views of the specimen. 



Fig. 7 c. Profile view of the same. 



Fig. 7 d. Front view of the same. 



Fig. 7 e. Enlargement of the beak of the dorsal valve. 



Fig. 7 /. View showing the elevation of the strice. 



Fig. 7 g. Several plications enlarged, showing the concentric striae. 



Position and locality. In the shale of the Niagara group at Lockport. 



{Colltetion of Col. Jkwett.) 



