4I« PALEONTOLOGY OF NEW- YORK. 



tral valve of the same species from Cumberland ( Maryland ). The impression of the 

 dorsal valve, which, from its corresjwnding cavity and other characters, I have 

 regarded as of the same species, is very distinctly marked in its renlforni muscular 

 impressions and the slight divergence of the vascular impressions in the lower part 



of the area. 



PLATE XCII. 



Fig. 2 a. The cast of the interior of a ventral valve, where the muscular impression is very 

 strongly marked and occupies a large part of the area of the valve. The central 

 upper portion, marked by the adductor muscles, is, in this and some other spe- 

 cimens, well defined and separated from the other parts. 



Fig. 2 6. A similar cast, where the cardinal angles are more extended and the muscular 

 impressions less strongly defined. Both tliis and the preceding specimen show the 

 imprint of the strongly striated cardinal area ; the first one having a flattened 

 space without striae in the place of the foramen, while this feature is less dis- 

 tinctly seen in the latter. 



Fig. 2 c. A fragment of a similar specimen, showing a process extending into tlie cavity 

 towards the beak of the valve. A mould made from the casts of this species shows 

 the foramen to be entirely closed, with a thickened process below and a cavity 

 extending beneath it towards the beak ; as if there may have been, at some 

 period of growth, a perforation of the apex. 



Fig. 3. The exterior of the ventral valve, showing the strongly striated surface. 



PLATE XCV. 



Fig. 9. This figure is an impression taken from a mould in sandstone, left by the solution 

 and removal of the shell. In several specimens of this kind, in different stages 

 of growth, the internal markings are precisely similar. The broad reniform mu- 

 scular impressions are strongly defined by an elevated rim ; and between these 

 and the median crest there are, on each side, other equally marked impressions, 

 which, with the flattened median crest, appear to have been the points of at- 

 tachment for the adductor muscles. Below and outside of these are vascular 

 impressions approaching those of Productus, which are strongly marked, but 

 not limited as the others. 



The direction of the vascular impressions towards the basal and lateral mar- 

 gins of the area is very direct, and the ramifications but slightly divergent ; a 

 character to be noticed in comparison with other species. 

 Geological position and locality. In the Oriskany sandstone : Albany and Scho- 

 harie counties ( New-York), and Cumberland ( Maryland ). 



Stropliodoiita vascularia ( n. s.). 



Flate XCIL Fiq. 4; and Plate XCV. Fia.lO : also Plate XCIIL Fio. 2 bSfc? 



Shell semielliptical, convex : cardinal extremities rounded. Ventral 

 valve, in the cast, showing a narrow crenulated area : muscular im- 

 pressions large, flabelliforra, the adductor muscles occupying an oval 

 space. The larger flabelliform area has the divisions ramifying and 

 diverging below, the narrow lines being the elevated parts and the 



