56 [ Senate 



scarcely geniculate in front : dorsal valve forming an inclined 

 plane from the hinge towards the front, near which it is ab- 

 ruptly deflected, giving the valve a deep concavity : hinge-line 

 equal to the greatest width of the shell ; lateral margins con- 

 tracted, so as to leave small auricular extensions at the extre- 

 mities of the cardinal border ; area sublinear, longitudinally 

 striate : interior distinctly granulose ; muscular attachments 

 strongly marked. 



Internal casts, with fragments of separate valves of tliis shell have been 

 seen : its general aspect is like that of Strophomena depressa, though its 

 internal muscular attachments often deviate considerably from those of 

 •well-marked specimens of that species. The ventral valve is also more re- 

 gularly arched and gibbous in outline than is usual in S. depressa ; and 

 it has not the abrupt genieulation in front, so characteristic of that shell. 



Geological position and locality. Oriskany sandstone, Albany county, 

 and Cumberland ( Md.). 



Chonetes complanata (n. s.). 



Pal. N.Y. Vol.iii, pi. 63, f. 1. 



Shell nearly semicircular, compressed? about two -thirds as long 

 as wide : ventral valve flat or concave : dorsal valve unknown ; 

 tubular spines of the cardinal margin directed obliquely out- 

 wards. Surface marked by fine, closely arranged (bifurcating'?) 

 strige, which appear to have been crenulated by closely arranged 

 concentric strise. Some of the specimens show distant imbricating 

 concentric lines of growth : interior finely granulose -, viscera , 

 impression large, uniform, not strongly marked. 



All the specimens seen of this rare species consist of internal and ex- 

 ternal casts of the ventral valve, from which it is impossible to make out 

 a complete diagnosis. The few remaining impressions of the row of tubular 

 spines along the cardinal margin are barely sufl&cient to show the presence 

 of these appendages, without clearly indicating their number, length, cur- 

 vature, etc. It may be recognized by its extreme flatness, finely striated 

 surface, a few distant lamince of growth, and great proportioiial width. 



Geological position a7id locality. Oriskany sandstone of Albany and 

 Schoharie counties. 



