206 PALEONTOLOGY OF KENTUCKY. 



Cypricardinia inflata, var. subequivalvis. HALL AND 



Cypricardinia inflata, var. subequivalvis, H. and W. 24th Regent's Report, p. 189 1872. 

 Cypricardinia inflata, var. subequivalvis, H. and W. 27th Regent's Report, pi. 11 1875. 



This species is described by Prof. Hall from a single specimen belonging to 

 the cabinet of the late Dr. James Knapp. At the time my plates were pre- 

 pared, said specimen was missing, and as thus the species was not represented 

 by any known specimen, I omitted it. Since then I have found, myself, two 

 fair shells of this species, and I therefore give here its description. 



Shell small, nearly equivalve, sub-quadrilateral ; beaks terminal ; cardinal 

 and basal margins sub -parallel; left valve slightly smaller, less convex, and 

 straighter than the opposite ; the post-umbonal slope distinctly angular, while 

 on the right valve it is sub-angular or rounded. 



Surface marked by about twelve to fourteen or sixteen strong, equal, lamel- 

 lose, concentric ridges. Prof. Hall based its name of equivalvis upon the fact 

 that in crushed specimens both valves appear equal, while good, not distorted, 

 individuals show the slight inequality of valves characterizing the genus. 



This shell resembles C. inflata, Conrad, but the valves are more nearly equal, 

 and the right valve is less inflated. 



Formation and Locality. The chert beds overlying the hydraulic cement rock of the Devonian 

 formation, in Jefferson county, Ky., and in Clark county, Ind. 



Genus Cypricardites. 



Conrad. 



Cypricardites, Conrad. Ann. Geol. Rep. N. Y. 1841. 

 Etymology : resembling the Ejenus Cypricardia. 



Shells ventricose, sub-orbicular or broad ovate in outline, with an external 

 flattened ligamental area ; cardinal teeth, four or five, short, oblique ; lateral 

 teeth, two or more, oblique; muscular impressions prominent, anterior one 

 single ; pallial line simple. Silurian. 



Synonyms: Cyrtodonta and Vanuxemia of Billings, and Palaearca of 

 Hall. 



Cypricardites halli. N.SP. 



Plate XX XIV., figures 1 to 6. 



Shell of medium size ; sub-triangular ; from moderately ventricose to gib- 

 bous ; both valves equally convex. Dorsal line almost straight, rounding at 

 its extremity into the anterior and posterior margins ; anterior margin slopes 

 down and backwards in a gentle curve, which is slightly inflected, at its center, 

 to the basal margin. The angle formed by the average direction of the an- 

 terior margin with the dorsal or hinge-line, measures about sixty degrees. 



