38 Geological Survey of Alabama. 



posterior end widely gaping, and has a wedge-shaped appearance. Tooth 

 strong, blunt below, sharp above ; hinge line short. 

 Locality. Baker's Bluff, Ala., Ferr. Sand Bed. 



The differences between this form and the Miocene P. porrecta, Con., 

 are very slight. Left valve figured. 



PRIMA, n. sp. PI. 6, fig. 14. 



Shell rotund, covered with rounded, close-set concentric stride ; poste- 

 rior with four radiating ribs ; anterior part smooth. Rostrum moderate, 

 narrow, rounded, with a concave, almost triangular space between it and 

 the body of the shell, the end curving upward ; ventral margin hollowed 

 out ; dorsal margin rising slightly above the hinge line. Cartilage pit, 

 minute, bent inward in left valve, which also has the posterior muscular 

 impression strongly defined by a rib on the inner side running to the dor- 

 sal margin ; hinge line nearly straight. 



Locality. Wood's Bluff, Ala. (lower bed). 



ALTERNATA, n. sp. PL 6, fig. 15. 



Shell small, moderately rotund, covered with very fine concentric lines ; 

 rostrum short, obtuse, rounded on top and angulated on dorsal margin ; 

 lines of growth becoming lamellar on its surface. Hinge line and dorsal 

 line of rostrum straight. Cartilage pit minute, narrow, oblique and 

 close under the beaks. 



Locality. Lisbon, Ala. 



Distinguished from the preceding species by its lack of radiating ribs, 

 smoother surface, and is much less rotund. Has a strong resemblance to 

 the recent Necera lamellosa, Sars. 



PHOLADOMYA CLAIBORNENSIS, n. sp. PI. 4, fig. 5. 



Shell exceedingly thin, pearly, concentrically ribbed, crossed by radial 

 lines, which are strong on the umbones ; beak high, very prominent close 

 to the anterior end of shell, anterior truncated abruptly ; posterior pro- 

 duced, flattened on the upper part; lunule long and narrow, smooth; 

 hinge raised, prominent. 



Locality. Lisbon, and beds at base of Claiborne Bluff, Ala. 



This species is close to P. Marylandica, Con., but appears to differ from 

 that species in height of beaks and their more anterior position, beside? 

 being abruptly truncated and posterior flattened. 



