No. 109.] 



51 



contracted below the extremities of the hinge ; hinge - line 

 straight, nearly or quite equalling the greatest width of the 

 shell, finely crenulated. Surface marked by distinct bifurcating 

 strise : interior granulose ; cast punctate. 



This species is nearly related to tlie last, but differs in the crenulated 

 hinge-line, and in having the internal surface more distinctly granulose ; 

 in consequence of which, the surface of casts always presents a punctate 

 aspect, from which it has received its name. 



GeoIogirMl jiosition and locality. Shaly limestone of the Lower Hel- 

 derberg, Albany, Schoharie, Herkimer and Oneida counties. 



Stroi . 



Strophomena ( Steophodonta) cavumbona ( n. s.). 



Pal. N.Y. Vol.iii, pi. 21, f. 1 - 3. 



Shell subsemicircular, from two- to four-fifths as long as wide, 

 usually contracted below the extremities of the hinge -line; 

 cardinal border sloping a little from the beaks, nearly or quite 

 equalling the greatest width of the shell : ventral valve concave 

 in the umbonial region and near the hinge, very convex in the 

 middle and towards the front : dorsal valve flat or concave ; 

 beak very small, scarcely elevated above the cardinal margin : 

 hinge-line straight, crenulated ; area linear, partly common to 

 both valves, transversely striate on the ventral valve ; foramen 

 small, narrow, closed. Surface marked by coarse irregular ra- 

 diating strise, which increase by implantation. 



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

 derberg, Albany and Columbia counties. 



