326 PROCEEDINGS OF THE ACADEMY OF 



falling into the genus Grammysia. That is, some of the species 

 presenting the aspect of that genus, excepting that the^^ want the 

 characteristic oblique ridge of the typical species. Until other 

 specimens can be examined, and more is known in regard to the 

 hinges of Grammysia and Sedgwickia, as well as that of the shell 

 under consideration, its generic relations cannot be satisfactorily 

 determined. 



Locality and position. — Upper part of the Cincinnati group of 

 the Lower Silurian, in Clinton County, Ohio. Mr. James's col- 

 lection. 



DOLABEA? CARINATA, Meek. 



Shell small, rhombic-cordate, very convex along the oblique 

 umbonal slopes, posterior margin apparently obliquely truncated; 

 posterior basal extremity more or less angular in outline ; basal 

 margin rounding and ascending obliquely forward from the pos- 

 terior basal angle ; anterior side extremely short, or with its mar- 

 gin descending and curving backward into the base from immedi- 

 ately in front of the beaks ; hinge line short, and a little inflected 

 so as to form a kind of small area or escutcheon behind the beaks; 

 beaks prominent, rather oblique, nearly terminal, strongly incurved 

 or subspiral, and distinctly compressed antero-posteriorly so as 

 to be sharply keeled on top, the keel being continued as a less 

 angular umbonal ridge backward and downward to the posterior 

 basal extremity; flanks in front of the umbonal ridge evenly 

 convex, while the space above and behind it, near the beaks, is 

 somewhat concave. Surface only showing obscure traces of lines 

 of growth. (Hinge and interior unknown.) 



Length, measuring obliquely from the posterior basal angle to 

 the most prominent part of the umbonal keels, 0.65 inch ; antero- 

 posterior diameter, measui'ing parallel to the hinge line (the speci- 

 men being defective behind), 0.40 inch ; convexity of the united 

 valves, 0.50 inch; length of hinge, about 0.30 inch. 



The only specimen of this species I have seen has lost, by ero- 

 sion, some portions of the posterior margin, so as to leave doubts 

 in regard to its exact outline, though it has the api^earance of 

 having been, when entire, more or less truncated behind. The 

 most remarkable features of the species are its prominent sub- 

 spiral, and very strongly carinated beaks, short hinge, and nearly 

 obsolete anterior side. Its front margins seem to have been a 



[March 19, 



