148 PALAEONTOLOGY OF KENTUCKY. 



dorsal valve is marked by fine, even, rounded striae, which are cancellated by 

 close concentric striae, and the same obscure concentric undulations, which are 

 often noticed on the ventral valve near the umbo. In general the shell is 

 readily recognized by its nearly flat form and by its fine, nearly equal striae. 



Formation and Locality. Occurs in the upper strata of the Devonian limestone at the Falls of 

 the Ohio, in Kentucky and Indiana, where the ventral valves are somewhat abundant. 



Strophodonta profunda. HALL. 



Plate XXIX., figure 26, and Plate XVII., figures 20 and 21. 



Leptaena pr ofunda, Hall. Pal. N. Y., Vol. 2, p. 61, pi. 21, figures 4 and 51852. 

 Strophodonta profunda, Hall. 20th Regent's Kep., p. 3691867. 

 Strophodonta profunda, Hall. 28th Regent's Rep., p. 151 1879. 

 Strophodonta profunda, Hall, llth Geol. Rep. of Ind., p. 289 1881. 



Shell large, broadly semi-oval ; width larger than length ; hinge-line greater 

 than greatest width of shell ; cardinal extremities slightly extended and sub- 

 auriculate, in casts of ten obtuse or rounded; shell concavo-convex. Ventral 

 valve, according to Prof. Hall's description, very convex ; this is not the case 

 with our shells. In our specimens the ventral valve is only moderately convex ; 

 in some individuals the central portion around the umbo is most convex, while 

 the balance is depressed, or even somewhat concave ; in other shells the central 

 portion is flat, or even somewhat concave, while the marginal portion of the 

 valve all around, from one extremity to the other, is strongly curved ; and, 

 again, in some specimens the whole valve, with the exception of the cardinal 

 angles, is regularly and prominently curved ; in these shells, the cardinal ex- 

 tremities are slightly deflected, and the surface between them and the umbo 

 gently depressed or concave. 



Hinge area narrow ; foramen triangular, of moderate size, and covered by a 

 strong deltidial callosity. 



Dorsal valve corresponding in its concavity with the convexity of the ventral 

 valve. Hinge-area narrower than that of the ventral valve ; foramen covered 

 by a callosity. Surface marked- by strong, large, radiating striae, which alter- 

 nate with four or five smaller striae, all of which, the smaller as well as the 

 larger, increase by intercalation. These radii are crossed by fine concentric 

 lines. In some specimens the smaller striae become stronger, forming the 

 larger and less regular striae. The specimen illustrated on plate 17, figure 20, 

 is one of the largest found near our city. 



Formation and Locality. Occurs, in the Niagara rocks in the quarries east of the city of Louis- 

 ville. It is not abundant. 



