176 PALEONTOLOGY OF NEW YORK. 



the lateral slopes of the pedicle-valve, and thus the outer face of the cones is 

 parallel to, and just within the surface of the brachial valve. It is such a 

 modification of the brachial apparatus as must necessarily ensue from the 

 variation in the contour of the shell. The character of the loop has not been 

 determined. 



Genus KARPINSKIA, Tschernyschew. 1885. 



PLATE LII. 



This designation has been applied* to a species, Karpinskia conjugula, Tscher- 

 nyschew, from the lower Devonian of the Ural Mountains, which is character- 

 ized by an elongate form, radially plicated and subequally convex valves. The 

 spirals have the same position as in Atrtpa, though the character of the loop 

 is still unknown. In the pedicle-valve are diverging dental plates, and in the 

 brachial valve a median septum. The vascular trunks are simple and direct, 

 extending to the anterior margin of the valves without branching. 



* Die Fauna des Unteren Devon am West-abhangre des Urals, pp. 48, 90, pi. vii, figs. 80, 86. 



