L. DENSATA, Conrad. 



OF CONCHOLOGY. 13 



LUCINID^. 

 LUCINA, Lam. 



L. Pennsylvaniea, Tuomej and Holmes, (wo^ iam.) — Pliocene 

 Foss. of S. Carolina, p. 56, pi. 18, fig. 3. 



This Miocene species is comparatively more elevated than L. 

 Pennsylvanica. The posterior margin is nearly direct, and ob- 

 tusely rounded or abrupt ; the sinus has a greater downward 

 slope, and the dorsal margins are much more oblique than in the 

 recent L. Pennsylvanica. 



CARDIID^. 



CARDIUM, Lin. 



C. (Trachycakdium) Emmonsii, Conrad. 



C. muricatum, Emmons, (not Lin.) — Geol. of North Carolina, 

 p. 301, fig. 233. 



This shell is shorter or comparatively more elevated than C 

 muricatum, with a thicker cardinal plate. In the figure the ribs 

 are also flatter on the back and furnished with broad scales, not 

 small tubercles as in C. muricatum. 



C. (Trachycakdium) Carolinensis, Conrad. 



Cardium muricatum, Tuomey and Holmes, (not Lin.) — Plio- 

 cene Foss. of South Carolina, p. 61, pi. 19, fig. 2. 



This species differs from C. muricatum in being less oblique, 

 and in being subequilateral, whilst the anterior margin is not 

 obliquely rounded, and the posterior ventral margin is almost 

 regularly rounded with the posterior margin ; the posterior ex- 

 tremity being undefined in consequence of a very slight trunca- 

 ture, whilst in C. muricatum this part is more abruptly rounded, 

 which gives a much longer proportional line to the umbonal slope ; 

 there are also fewer ribs in the present species and a much deeper 

 serration to the anterior margin of the valves. It is a smaller 

 species than C. muricatum. 



VENERID^. 



lyfEROENAEIA, Sclium. 



M. percrassa, Conrad. 



Description. — Cordate, profoundly ventricose and thick in sub- 

 stance ; humped or subangular below the umbo, radiato-plicate ; 

 disk rough with prominent waved lines of growth ; posterior mar- 

 gin obliquely truncated, posterior area depressed, with a longi- 



