No. 109.] 



49 



Strophomena ( Strophodonta) headleyana ( n. s.). 



Pal. N.Y. Vol. iii, pi. 20, f. 1 & 2. 



Shell nearly semicircular, about three-fourths as long as broad : 

 ventral valve very concave especially near the front, sometimes 

 depressed-convex at the beak ; beak scarcely distinct from the 

 margins of the area : dorsal valve depressed at the umbo, and 

 very convex towards the front ; beak not extending beyond the 

 cardinal margin : hinge-line equalling the greatest width of the 

 shell, crenulated ; area somewhat wide, and marked by trans- 

 verse striae produced by. the continuation of the crenulations 

 from the hinge-line across its surface ; foramen narrow, closed. 

 Surface marked by coarse, sharply elevated striae, which increase 

 chiefly by implantation, and present a peculiar irregularly 

 waved appearance. 



Geological position and locality. Shaly limestone of tBe Lower Hel- 

 derberg, Albany and Schoharie counties. 



Strophomena headleyana. 



f Senate No. 109.] 4 



