42 PLEIOCENE F.OSSILS. 



AKCA TRANSVERSA.— Say. 



Plate XV., Figs. 6 and 7. 



Area Transversa, Say., Jour. Ac. Nat. Sci. Vol. II., p. 259. 



Area Transversa, Say., Foss. Shells. Ter. For., No. 2, p. 15, tab. I, fig. 2. 



A. testa elongato-ovata ; latere buccali breviore, subangulato ; latere anali elongate-, angulato • 

 area ligamenti angusta sulcata, umbonibus depressis, approximatis. 



Description. Shell elongately ovate ; buccal side shorter, somewhat angulated above ; 

 anal side elongated, angular ; area of the ligament narrow, furrowed. 



The young shell, as described by Say, has the right valve with the ribs all nodulous; in 

 the left only those on the buccal side are thus ornamented. With age these characters are 

 rendered less striking, and the shell becomes less regular. 



The elongated form of this shell distinguishes it pretty well from its congeners. It is, 

 however, very variable, yet through all its variations the undulating depressions upon the 

 umbones, which to their very points, can always be perceived. Fig, 6 represents a variety 

 which is well marked both in the recent and fossil state. The umbones are less compressed, 

 and the whole shell more rounded and irregular. 



Plate XV., Fig. 6. Exterior of left valve and hinge and teeth of right valve. 

 " 7. End view, showing outline of hinge and umbones. 



Locality. Darlington District. 



Museum, College of Charleston. 



