CLINTON QKOUP. 



I 



Position and locality. This species occurs in the calcareous layers above the lower green 

 shale at Reynale's basin, at Medina, and other places. It has not been recognized in the upper 

 part of the group. 



445. 20. LEPT^NA PROFUNDA (n. sp.). 



Pl. XXI. Fig. 4 a, h. 



Shell large, semioval, much wider than high ; hinge-line extended beyond the width of the 

 shell ; ventral valve profoundly concave (the depth being | of an inch), bending very abruptly 

 upwards ; surface marked by fine unequal striae ; interior surface papillose or punctate, de- 

 pending on the degree of weathering. 



This shell differs greatly from the last, as also from any other species of the group, by the 

 great concavity of the ventral and convexity of the dorsal valve. The specimens are usually 

 very imperfect, and the external characters obscure. The one figured is the interior of the ventral 

 valve, which preserves the hinge-line, showing the projecting, grooved and bidentate process 

 through which the pedicel passed. The interior surface is finely striato-punctate ; but the 

 specimens being mostly weathered, it varies in the appearance of the markings. 



Fig. 4 a. The interior of the ventral valve, which is worn on the upper part, and striato-punctate 



below. 

 Fig. 4 5. A portion of the surface enlarged. 



Position and locality. This species is known only in the upper limestone of the group at 

 Lockport, Niagara county. {State Collection. Collection of Col. Jewett.) 



445. 20. LEPTiENA PROFUNDA 1 (young SHELL 1). 



Pl. XXI. Fig. 5 a, b, c. 



Dorsal valve very convex, flat near the hinge, and bending abruptly downward and inward 

 towards the margin ; surface marked by large striae alternating with four or five smaller ones, 

 which are all crossed by fine concentric lines. 



The shape of this young shell resembles the preceding so nearly, that I am inclined to unite 

 them, though I have had no good opportunity of examining the surface of individuals in the 

 intermediate stages of growth. The shell (the dorsal valve) is extremely convex, corresponding 

 in this respect to the deep concavity of the large ventral valve fig. 4. 



Fig. 5 a. Outer surface of specimen. 5 b. Profile view of same. 5 c. The striae enlarged. 



Position and locality. In the lower limestone of the group, corresponding in position to the 

 Pentamerus oblongtis, Reynale's basin, Niagara county. {Collection of Col. Jewett.) 



