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 tlie 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 this shell have been 

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

 internal muscular attachments often deviate considerably from those of 

 well-marlied 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 geniculation in front, so characteristic of that shell. 



Geological positioji and locality. Oriskany sandstone, Albany county, 

 and Cumberland ( Md.). 



Chonetes complanata (n. s.). 



Pal. N.Y. Vol. iii, pi. G3, f. 1. 



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

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

 tubular spines of the carclinal margin directed obliquely out- 

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

 striae, w^hich appear to have been crenulated by closely arranged 

 concentric strice. 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 sufficient 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 lamina) of growth, and great proportional width. 



Geological position a7id locality. Oriskany sandstone of Albany and 

 Schoharie counties. 



