31 St. Maurice and Claiborne Pelecypoda 31 



Pinna cawcawensis.n. sp., PI. 17- Figs, i, 2. 



General shape and size indicated by fig. i ; surface of the 

 valves with numerous radii above, well defined ; below with con- 

 centric undulations upon which are superimposed even more radi- 

 ating costae than above, but they are less distinct. Zigzag bases 

 of fimbriate folds upon the ribs precisely as in the living sq^iamos- 

 issiviaV\\-\\.., or seinimidal^^ira. (pi. 16, figs. 12-13). 



In outline this is VAlq: jacksonia7ia Dall, or argentea Con. 

 The Claiborne sand, Jackson and Vicksburg specimens, however, 

 so far as our specimens show, had no well-developed dermal, 

 semicircular spines, and too, the radii on the lower portion of the 

 shell are fewer than above, and of uncertain direction. 



Type and specimens figured. — Deposited in the Paleont. Mus. 

 Cornell Univ. 



Horizon. — St. Maurice Eocene. 



Locality. — Five miles N. of Orangeburg, Columbia Road, 

 S. C. 



Pinna sp. 



Several fragments of a Pinna very similar in form to caivcazv- 

 ensis, argentea 2inc\. jacksoniana are in our collections from the 

 Claiborne sand beds. Their surface characters are too imperfect 

 to admit of specific description. 



Aldrich (Bull, i, Geol. Surv. Ala. 86, p. 49) refers to Pinna 

 "very large" at Coffeeville. Ala. 



l\lotliolus cawcawensis, n. sp., PI. 17. Figs. 3, 4 



Specific characterization . — Size and form as figured ; inflated 

 along a well defined umbonal ridge anteriorly, becoming less ven- 

 tricose from the center of the shell posteriori}'' ; posterior broadl}^ 

 and evenl}' rounded ; exterior with generally fine but more or 

 less variable concentric lines of growth. 



In general outline this shell recalls A^. ducatelii of Maryland 

 Miocene, but is broader posteriorly and without the remarkable 

 concentric fold on the anterior of that species. 



It is far less angulated as to umbonal slope and posterior ex- 

 tremit}^ than cretacea of Conrad. 



