28 Cincinnati Society of Natural History. 



of the pedicel valve, and the remarkably long cardinal process 

 of the brachial valve, together with the strong crural plates, 

 are distinctly shown. Anterior to the cardinal process the 

 shell is thickened interiorly, forming a rather wide though 

 low elevation, narrowing anteriorly, and disappearing before 

 reaching the middle of the valve. 



West Union bed, at the Spring on Big Salt Lick creek, 

 one mile south of Glen Springs, in Lewis county, Kentucky. 



The very strong and prolonged cardinal process suggests 

 that of some forms of Triplecia, but it is not divided anteriorly, 

 and the deeply impressed muscular area of the pedicel valve 

 gives unmistakable evidence of the real affinities of this 

 shell. 



PenTx\merus divergens, sp. nov. 

 Plate 1, Figs. 5 A-E; Plate II, Figs. 17 A, B. 



Shell rather small. In one specimen, preserving both 

 valves but considerably deformed by pressure, the length of 

 the brachial valve is 26 mm. ; the width, 18 mm. ; the length 

 of the pedicel valve is estimated at 29 mm. ; and the original 

 thickness of the complete shell, at 10 or 11 mm. The gen- 

 eral outline of the shell is ovate. The anterior outline is 

 rounded, and the postero-lateral margins are flattened and 

 converge toward the beak. This flattening is most conspicu- 

 ous in case of the pedicel valve, where it results in a strong 

 lateral compression of the posterior parts of the valve. The 

 anterior margin of the shell is rounded, occasionally with a 

 faint indication of the trilobation seen in other species of this 

 genus. In the deformed specimen, mentioned above, the mid- 

 dle third of the brachial valve is raised slightly above the 

 remainder. The margins of the delthyrium of the pedicel 

 valve slope backwards from the plane of separation of the 

 valves at angles varying from 45 to 60 degrees, causing the 

 beak of this valve to be divergent from the remainder of the 

 shell. The brachial valve is moderately convex, the beak 

 curving over the lower part of the delthyrium of the pedicel 

 valve. 



28 



