76 LAND AND FRESH-WATER SHELLS OP N. A. [pART IV. 



resembles Thorntonii herein described, but is a much smaller species, 

 with a smaller aperture and compressed whorls. All the specimens 

 before me are more or less angulate on the periphery. None have 

 bands. The aperture is about two-ninths the length of the shell. I 

 name this after Mr. Postell, to whom I am indebted for specimens of 

 this and many other new species of MoUusca. — Lea. 



This species is closely allied to infrafasciatum but may be 

 distinguished by its whorls being more flattened, and by its 

 narrower form. 



20. P. incurvum, Lea. 



Trypnnosfoma inairvum, Lea, Proc. Acad. Nat. Sci., p. 171, 18G2. Jour. Acad. Nat. 

 Sci., V, pt. 3, p. 286, t. 30, f. 109. Obs., ix, p. 108. 



Description, — Shell carinate, conical, rather thin, horn-color ; spire 

 somewhat elevated ; sutures regularly impressed ; whorls eight, flat- 

 tened, obscurely striate below ; aperture rather small, rhombical 



whitish within ; outer lip acute, extremely sinuous ; colu- 



' Fig. 1«. 



mella vei-y much twisted. 



Habitat. — Florence, Alabama; Rev. G. White. 



Diameter, -37; length, -89 of an inch. 



Observations. — Among the Melanidce sent to me by Mr. 

 White, I found three specimens of this species which, being 

 near to Thorntonii, herein described, evidently was supposed 

 to be the same species. It is, however, a smaller, thinner and more 

 slender species, and the remarkable sinuous edge of the outer lip at 

 once marks the difference. The inward curve, starting at once in that 

 direction from the suture, turns forward before it reaches the periph- 

 ery of the whorl and again curves to the base, making a complete 

 sigmoid curve. The aperture is about one-third the length of the 

 shell.— Lea. 



Tliis species resembles the last but is very distinct in the 

 incurved tip. It differs from infrafasciatum by the same 

 characters as Postellii. 



