124 MR. CONRAD'S DESCRIPTIONS 



CORBIS. 



C. STAMINEA. PI. 13, fig. 20. — Suboval, convex, thin, with lamellteform concentric strise, about 

 thirty-seven in number ; posterior side with a slight fold ; beaks medial. Length 1. Rare. 



LUCINA. 



L. MississiPPiENSis. PI. 12, fig. 22.— Orbicular, thin and fragile, with minute obsolete radiating lines; 



anterior side shortest, the margin obliquely truncated, angular above and elevated ; inferior margins 



rounded ; posterior end obtusely rounded ; lunule profound ; cardinal and lateral teeth wanting. 



Length 9-10. Height |. 



This species very much resembles L. suhvexa of Claiborne, but wants the 



impressed line on the posterior side. Rare. 



L. PERLEvis. Orbicular, with lamellseform concentric lines, and very minute obsolete radiating lines, 

 closely arranged ; beaks medial ; posterior end direct ; cardinal teeth small. Length 4-10. Height 

 rather less. Very rare. 



LORIPES. 



L.'? TURGiDA. PL 12, fig. 23. — Suborbicular, very thin and fragile, with minute concentric lines; beaks 

 medial ; umbo and summit prominent ; margins regularly rounded. Height 6-10. Length rather more 

 than 5-10. 



L. EBURNEA. PI. 12, fig. 24. — Suborbicular, slightly oblique, convex, with minute closely arranged 

 concentric lines, and a few larger impressed lines ; posterior margin truncated, direct ; anterior end 

 and anterior basal margins regularly rounded ; posterior basal margin obliquely truncated ; beaks 

 nearest the posterior end. Length 6-10. Height 6-10 nearly. 



CORBULA. 



C. iNTASTRiATA. PI. 12, fig. 31. — Subtriangular, inflated, rostrated posteriorly ; within with fine radiating 

 lines. Length 4. Very rare. 



C. ALTA. PI. 12, figs. 33, 34, 35. — Subtriangular, profoundly elevated, slightly oblique; larger valve 

 ventricose ; summit very prominent ; umbo broad ; hinge plate thick, with large teeth ; smaller valve 

 somewhat flattened, angular over the umbonial slope. Length 6-10 nearly. Height 6-10. 



Occurs abundantly about eight miles North East of Vicksburg, and always 

 water- worn. 



C. ENGONATA. PI. 12, fig. 30. — Triaugukr, inequilateral, small ; valves nearly or quite equally convex, 

 and with angular concentric ridges; posterior slope concave ; umbonial slope carinated. Length 3-10. 



CHAMA. 



C. MISSISSIPPIENSIS. PI. 13, figs. 21, 27. — Suboval, irregular, adhering; larger valve ventricose, with 

 numerous irregular radiating lines, squamose inferiorly ; upper valve with numerous concentric lines, 

 with numerous small scales. Length |. Height 6-10. 



Rare, and occurs on Dr. Smith's plantation, six miles North East of Vicksburg. 



