208 MR. CONRAD'S DESCRIPTIONS OF 



I cannot say certainly that it is the same with the C. alta. These shells are 

 situated below the indurated marly beds which contain the remains of crabs, as I am 

 informed by J. D. Anderson, Esq., of Vicksburg, who collected the specimens. The 

 stratum near Dr. George Smith's plantation, about six miles N. E. of Vicksburg, in 

 which I found the Natica Mississippiensis and Corbula alta, is identical with that of 

 Vicksburg to which I have alluded. 



KECENT SHELLS. 

 SILIQUA, Megerle. Leguminaria, Schum. 



S. FLORiDANA. — Equilateral convex ; posterior side narrower and more acutely rounded than the anterior ; 

 basal margin slightly contracted or arched ; colour purple, umbo whitish ; epidermis olive with two 

 narrow whitish rays on the posterior side; rib marked by a broad purplish brown ray. 



SoLEcuKTis Fragilis. — Var. nob. Proceedings, Vol. iii. p. 24, fig. 10. 



Locality. Inhabits Egmont Key, Tampa Bay, Florida. 



LYON SI A, Turton. 



L. FLORIDANA. — Very inequilateral, ovate-oblong, thin, fragile, inflated ; posterior side produced, slightly 

 recurved, narrow and direct at the extremity, a slight furrow on the submargin of the hinge ; 

 epidermis extremely thin, white, with fine radiating lines. 



OsTEODESMA HYALiNA ? — tiob. Proceedings, Vol. iii. p. 24, fig. 7. 



This species is larger than L. hyalina, much longer in proportion, narrower 

 posteriorly, and has more distinct radiating lines. 



CRYPTOMYA, Con. 



An equivalved, equilateral, bivalve, closed or very slightly gaping, the hinge 

 similar to that of My a ; pallial impression without a sinus, but forming a right angle 

 posteriorly. 



Sph^nia californica. — nob. Journ. Acad. Nat. Sci , vol. vii. p. 234, PL 17, fig. 11. 



This shell was incorrectly referred to SpHiENiA, and cannot with propriety enter 

 the genus Mya. " The form of the pallial impression, and the valves being nearly 

 or quite closed, prove that the animal inhabiting this shell differs from that of Mya.'' 



DONAX. 



D. protracta. — Elongated ; anterior side produced, acutely rounded at the extremity ; hinge and basal 

 margins parallel ; hinge margin straight, scarcely oblique ; posterior side cuneiform, distinctly striated, 

 acutely rounded at the extremity ; disk widely contracted between umbo and base, arching the basal 

 margin ; surface with crowded minute radiating lines ; colour variable, light red or purple, more or 

 lesj rayed; interior red or purple with a white margin; margin crenulated. 1 1-16. i. 



