New Species of Fossils from Hudson River Group. 27 



equal to the greatest length of the shell, but shorter than the 

 height of the shell. Anterior, posterior, and basal margins 

 rounded below the wings. Left valve rather highly and 

 broadly convex, umbonal region prominent and distinctly 

 defined by the sulcus separating it from the posterior wing, 

 but obscurely defined anteriorly. Beak near the anterior part 

 of the hinge, acute, and curves forward over the cardinal line, 

 beyond the beak of the other valve. Anterior wing small ; 

 posterior wing triangular, flat ; extremity acute, and margin 

 concave. Surface marked by crowded, wrinkled, concentric 

 striae that become closer and closer toward the margin of 

 the shell. The right valve is about half as convex as the 

 left, and the umbonal region is quite as clearly indicated. 

 Surface smooth. 



This species is quite variable in size, as shown by the illus- 

 trations, and even they do not represent either the largest or 

 smallest specimens. The only difference observed in the 

 growth of the shells is that the wings are proportionally 

 slightly more developed with age. It would seem from the 

 surface ornamentation of the shell to have its nearest affinity 

 with P. corrngata, James, from the upper part of the Hudson 

 River Group, though the ornamentation on that shell is more 

 conspicuous, and the striae less crowded than on this. It is 

 distinguished, however, from P. corrugata by greater height 

 in proportion to its length, greater convexity of the valves, 

 smaller wings, and more extended beak of the left valve. 

 This is a rare species, occurring in the middle part of the 

 Hudson River Group, in the higher stone quarries, on the 

 hills about Cincinnati. The specimens illustrated belong to 

 the collections of the authors. 



Technophorus faberi, S. A. Miller. 



Plate z, Fig. 20, left valve of a large specimen. 



This species was described from complete casts, and from 

 shells having the posterior wing-like extension broken away, 

 and even the point of the postero-basal extension was slightly 

 broken off. We are able now to figure a complete valve 



