528 NORTH AMERICAN INDEX FOSSILS. 



concentric striae, often becoming strong undulations, and, on the 

 body of the shell, with distinct radii which are absent from the 

 anterior end and cardinal slope. Ligament external. Devonic. 

 458. P. radiata (Conrad). (Fig. 716.) Devonic. 



a b 



Fig. 716. Pholadella radiata ; a, b, right valves ; c, d, left valves. 

 (Pal. N.Y., V.) 



Basal margin slightly sinuous, owing to the depression extend- 

 ing from beak to base. 



Hamilton : New York, Pennsylvania, Maryland. Ithaca : Penn- 

 sylvania. 



CXXV. Cimitaria Hall. 



Very elongate, with anterior and strongly incurved beaks, 

 short and rounded anterior end and long and truncate posterior. 

 Umbonal slope well defined. Surface crossed by strong concen- 

 tric growth lines and marked by very fine radial striae and by a 

 depression extending somewhat posteriorly from the beaks to the 

 base. Lunule present. Ligament external. Hinge without teeth. 

 Devonic. 



459. C. corrugata (Conrad). (Fig. 717, d.) Devonic. 

 Posterior cardinal slope comparatively wide, marked by one or 



several radial folds. Body of shell marked by concentric undu- 

 lations. 



Hamilton : New York. 



460. C. recurva (Conrad). (Fig. 717, a, b.) Devonic. 

 Differs from C. corrugata in its more curving outline and more 



rounded posterior extremity. Type of genus. 

 Hamilton : New York, Pennsylvania. 



461. C. angulata Hall. (Fig. 717, c.) Devonic. 

 Umbonal ridge strong and angular. Concentric striae regular 



and covering the whole shell. 

 Chemung : New York. 



CXXVI. Pholadomya Sowerby. 

 Shell thin, translucent, subovate, ventricose, equivalve, gaping 

 posteriorly and sometimes anteriorly. Anterior side short, rounded . 



