258 Thikty-fifth Report on the State Museum. 



LmiOPECTEN SOLOX. 



Lyriopecten solox, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explanations: 

 PI. 24, fig. 5. Jan., 1883. 



Shell of medium size, nearly circular ; transverse axis not inclined 

 to the hinge-line; margin regularly rounded, and sloping somewhat 

 abruptly into the byssal sinus. Right valve moderately convex. 

 Left valve unknown. Hinge-line straight, length about one-half 

 the diameter of the shell, extending farther on the anterior side. 

 Beak obtuse, rounded, central, not rising above the hinge-line, di- 

 rected slightly forward; umbo ample. Posterior ear triangular, 

 defined by its flattened surface, and the rapid umbonal slope; 

 margin concave; extremity rectangular. Anterior ear imperfect, 

 but showing a very deep and narrow byssal sinus. 



Test marked by numerous fine, angular rays, which are arranged 

 in about 40 regular, rounded plications, composed of fascicles of 

 finer rays, with defined interspaces. Finer obscure rays mark the 

 umbo, and the posterior ear shows three or four hundred undula- 

 tions with lines of growth. Interior not known, except *the liga- 

 mental area, which is narrow, and makes an inflection of the hinge - 

 margin of the ears. 



The dimensions of the right valve described are as follows : 

 height 43 mm., longitudinal diameter 42 mm. , and hinge-line ap- 

 parently about 25 mm. 



This species differs from L. Polydorus by its circular outline, con- 

 vexity, obtuse beak, ample umbo and surface characters It differs 

 from L, magnifiers and L. macrodontus in the greater convexity 

 of the valve and fullness of the umbo, as well as in the character of 

 the rays. It is also much smaller than those species. 



Formation and locality. In a fine semi-calcareous, argillaceous 

 sandstone (lying above the conglomerate ?) of the Upper Chemung 

 group, near Panama, Chautauqua county, N. Y. 



