P. E. Raymond — Fauna of the Chazy Limestone. 373 



Cyrtodonta solitaria sp. nov. 



Shell roughly triangular, the beak a little behind the ante- 

 rior end. Hinge line short. The anterior margin is narrow 

 and rounded, the base long and straight, incurved at about 45° 

 with the hinge. Posterior regularly rounded. Shell only 

 moderately convex, the slope to the posterior end gradual and 

 to the front nearly flat. 



Length 15 mm ; height 12'5 mm . Surface marked by concen- 

 tric lines of growth. 



Locality. — Ledge in pasture near Tracy Brook, Chazy, New 

 York. The type is in the Yale collection. 



Whitella canadensis sp. nov. 



Shell small, convex, subrectangular in outline. A promi- 

 nent ridge extends from the beak to the lower posterior corner. 

 From this ridge the slope to the cardinal and posterior margins 

 is abrupt, while there is little slope to the front until a point 

 in front of the beak is reached, when the slope is suddenly 

 deflected. The surface is marked by concentric undulations. 



Locality. — Aylmer sandstone, Aylmer, Quebec. 



Clionychia marginalis sp. nov. 



Both valves moderately convex, the umbones somewhat 

 depressed, but increasing rapidly in height^ the greatest thick- 

 ness of the valves being at about one-third the distance from 

 the beak to the lower margin. Hinge line short. The poste- 

 rior margin is broadly rounded, the lower margin semi-circular. 

 The front is almost straight. The greatest convexity is along 

 a line parallel to the front. The posterior and lower slopes 

 are gentle, but the front slope is abrupt, almost 90° with the 

 plane of union of the valves. The surface is marked 1 by very 

 line concentric striae. 



One specimen is 20 mm long and 26'5 mm high. 



Loccdity. — Chazy and Yalcour Island, New York. The 

 type is in the Yale collection. 



Ambony chia f curvata sp. nov. 



Shell large, both valves very strongly convex, especially 

 along the region of the front and middle of the valves. Beaks 

 small, incurved, directed a little forward. Anterior slope 

 abrupt and overhanging. Posterior and bottom slopes rather 

 steep. Posterior wing short. The posterior margin is almost 

 straight. The anterior margin is regularly curved. The 

 length and breadth are nearly equal. 



Am. Jour. Sci. — Fourth Series, Yol. XX, No. 119.— November, 1905. 

 26 



