1048 NEW YORK STATE MUSEUM 



Camarotoechia hudsonica sp. nov. 

 Shell in form and size resembling 0. neglecta of the 

 Niagaran, but differing in structural details. Pedicle valve 

 less convex than brachial, with a pointed incurved beak. The 

 valve is proportionally more, convex at the beak, with the sides 

 rather abruptly bending down. The valve broadens rapidly 



Fig. 8 Camarotoechia hudsonica 



forward, having a triangular appearance. Lateral slopes below 

 the beak slightly concave, median depression beginning about 

 halfway from the beak, at first faintly defined but becoming 

 more pronounced toward the front, where it produces a marked 

 deflection of the frontal margin. It is never very much accen- 

 tuated, but contains three pronounced angular plications which 

 toward the front are separated by interspaces nearly twice their 

 width. A plication of similar strength limits the depression 

 on each side, becoming progressively fainter outward. Thus 

 there are from four to five medially depressed ones. At the 

 beak the plications have the form of distinct threadlike, rounded 

 striae. The concave lateral slopes are not plicate, but radiating 

 striae have been observed in some specimens. 



Brachial valve uniformly convex, convexity greater than that 

 of pedicle valve. Beak closely incurved. In the center of the 

 valve four angular plications become more elevated from the 

 center forward, the central two being most elevated, rising at 

 times so much above the others as to give the fold a biplicate 

 aspect. On either side of these are two fainter ones, with, gen- 

 erally, indications of a third one near the margin. At the beak 

 these plications are threadlike, rounded and uniform, except at 

 the margin. 



Surface of valves marked by very fine, threadlike concentric 

 Hues, which are elevated and are equally strong on the plica- 

 tions and interspaces. They are separated by spaces some 



