92 TRANSACTIONS OF THE WAGNER FREE 



This shell most nearly approaches the preceding in outline, but can 

 be distinguished by its broadly swelling anterior border, its greater height, 

 and the form of the sinual inflection. 



Semele perlamellosa, nov. sp. Fig. 23. 



Shell thin, transversely elongated, oval, about equilateral ; beaks cen- 

 tral, acute, not prominent; right valve with a vertically incised, lamellar, 

 cardinal-tooth, which is followed by the very oblique, and broadly opening 

 cartilage sulcus ; dental fissure in left valve narrow, apparently duplicated ; 

 lateral teeth subcentral ; surface covered with numerous, regularly placed, 

 elevated lamella? of growth, which are gently angulated on the posterior 

 slope. 



Length, 2.8 inches ; height, two inches. 



A single specimen from the banks below Fort Thompson. 



Venus rugatina, nov. sp. Fig. 24. 



Shell ventricose, subcircular, appearing on its inner aspect much like 

 Isocardia, with a prominent anterior projection, corresponding to the 

 lower boundary of the deeply-impressed lunule ; hinge-line in each valve 

 with two prominent, transversely projecting, cardinal teeth, and a third 

 (posterior) oblique one, which, in the left valve, is separated from the 

 median tooth by a deep.'obliquely directed, dental sulcus ; the anterior 

 tooth in the left valve deeply grooved above, and preceded by a dental 

 papilla ; posterior lateral teeth not prominent ; surface covered with very 

 numerous, sharply-defined, imbricated lines of growth, which at nearly 

 regular intervals are marked off by lines of special prominence, imme- 

 diately below which the normal lines are least closely crowded ; number 

 of prominent lines twenty-five and upward ; number of normal lines 

 between these from six to eight ; border crenulated, the crenulation 

 extending under the lunule. 



Length, 2.5 inches; height, 2.1 inches. 



Abundant in the banks below Fort Thompson. 



Closely resembles the recent Venus nigosa, but may be readily distin- 

 guished by the greater interval separating the more prominent lines. 



Cardium Floridannm, nov. sp. Fig. 25. 



Shell obliquely cordate, upright, posterior slope somewhat depressed, 

 flattened ; beaks elevated, with the apex turned gently toward the anterior 

 margin ; left valve with a deep pit immediately under the apex, in front 

 of which is a prominently projecting pointed tooth ; two pyramidal 

 lamellar teeth, underneath which are corresponding dental pits ; right 

 valve with the lateral teeth underlying the dental pits ; hinge-line raised 

 anteriorly into a flattened vertical plate, which ascends beyond the apex 

 of the beak. 



