FOSSILS OF THE HUDSON EIVER GROUP. 91 



With Sedrjwickia we believe them to have little or no affinity ; still, from 

 the very heterogeneous nature of the material referred to that genus, we 

 are somewhat at a loss to know of what the grouj) consists, until the 

 characters of the types can be ascertained. 



CUNEAMYA MlAMIEXSIS (ll. Sp.). 

 Plate 2, figs. 9, 10. 



Shell small, cuneiformly ovate in outline, largest at the anterior end, 

 tapering, and somewhat pointed posteriorly. Valves very ventricose in 

 the anterior part and on the umbonal region, approaching gibbosity ; 

 beaks proportionally large, strongly enrolled, projecting prominently 

 above the hinge line, and nearly or quite terminal, varying in this latter 

 feature slightly in different individuals ; cardinal line very little curved, 

 extending more than half the length of the shell posterior to the beaks ; 

 escutcheon distinct, but not strongly marked; lunule very distinct, mod- 

 erately large, and deeply impressed, the margins being somewhat angu- 

 lar; anterior end of the shell inflated, the border rapidly sloping back- 

 wards from the lower extremity of the lunule to the basal line, into 

 which it gradually fades ; basal line moderately arcuate, with a broad, 

 shallow sinus about midway of its length, corresponding to the very 

 shallow depression of the surface of the valve ; posterior end acutely 

 rounded, sloping rajjidly above from the extremity of the hinge line to 

 near the point of greatest length ; posterior umbonal ridge very promin- 

 ent and rounded on the anterior two-thirds of the shell, gradually becom- 

 ing less prominent posteriorly; cardinal slope moderately concave ; an- 

 terior umbonal region very full and abruptly rounded, and declining to 

 the anterior margin of the valve, giving to this end of the shell a some- 

 what truncated aspect ; central portion of the valves slightly depressed, 

 forming a broad, shallow, and undefined sulcus, extending from the 

 beaks, and gradually widening to form the broad, shallow sinus of the 

 basal line. 



Surface of the shell marked by numerous, rather fine, or proportionally 

 small, even, concentric plicse or ridges, extending from the margin of the 

 lunule to beyond the posterior umbonal ridge, becoming obsolete on the 

 cardinal slope. The number and size of these concentric furrows and 

 ridges vary considerably in dififerent individuals of the species. 



Specimens of this species were received from persons in Ohio, with the 

 understanding that it had been described by Mr. INIeek as Grammysia 



