Silwian Fossils. 23 



also the absence of fasciculation among the radiating striae. 

 Its relations to the species described by Hall as Stropheo- 

 donta prisca are unknown, but Whitfield and Hovey interpret 

 the type specimen as an imprint of the ventral valve of a spe- 

 cies of StropJwuclla. In that case our specimens are distinct. 



SCHUCHERTELLA COXFERTUS, Sp. nOV. 

 Plate II, Figs. 13 A, B. 



Shells attaining a length of 18 mm. and a width of 26 mm. ; 

 very flat and thin. The pedicel valve is gently and evenly 

 convex, the convexity usually not exceeding 2 mm. The 

 brachial valve is almost flat, the convexity toward the beak 

 being almost imperceptible ; occasionally, it is even slightly 

 concave. The postero-lateral angles vary from 75 to 90 de- 

 grees. The dental lamellae diverge at an angle of 75 to 85 

 degrees and extend between 1.5 and 2 mm. beyond the hinge- 

 line. There is no evidence of a broad deltidium arching over 

 the delthyrium. ^Muscular area not distinctly outlined. Crural 

 ridges of the brachial valve distinct, forming a crescent-shaped 

 elevation. At the beak there are two, apparently rather 

 'narrow elevations which represent the cardinal process. The 

 surface of the shell is marked by numerous radiating striae, 

 of which there are 5 in a width of 2 mm. at a distance of 10 

 ■mm. from the beak ; in larger shells the number may be 

 reduced to 6 in a width of 3 mm. These striae are sub- 

 equal in size except at those distances from the beak at which 

 additional striae are intercalated, where the striae are alternately 

 larger and smaller. 



West Union bed. In the bluff northwest of ^lartins. in 

 Lewis county, Kentucky. 



The generic relations of this shell are uncertain. The 

 very distinct convexity of the pedicel valve, and the flatness 

 or even slight concavity of the brachial valve apparently ex- 

 clude it from any close relationship with Schucheriella siib- 

 planiis, in which it is the brachial valve which is distinctly 

 convex and in which the pedicel valve is distinctly less con- 



23 



