lis AMERICAN JOURNAL 



" Sirepliobasis, Lea. — Shell cylindrical ; aperture subquad- 

 rate ; columella thickened and retro-canaliculate below. 



" Operculum commencing spiral, corneus. 



" The mollusk, for which I propose this genus, was sent to 

 me by Wm. Spillman, M. D., of Columbus, Miss., and I have 

 before me over a dozen specimens from a third to nearly an 

 inch in length. The very great number of species of the genus 

 Melania makes it desirable to eliminate any group, with char- 

 acters sufficiently distinct to permanently recognize it. The 

 very remarkable retrorse callus at the base of the column, caus- 

 ing a lateral sinus, is characteristic of this genus. " 



Next we have the genus Goniohasis^ intended to include 

 most of the vast residue of species not previously eliminated. 

 This genus, proposed in Proc. Acad. Nat. Sciences, May 1862, 

 is described as follows : — 



" Goniobisis, Lea. — -Shell conical or fusiform. Aperture 

 subrhomboidal, subangulate below. Columella thickened 

 somewhat above. Operculum commencing spiral, corneus. 



" In my paper on the genus Trypcmostoma, proposed by me, 

 (Proc. Acad. Nat. Sci., 1863, p. 169,) I mentioned the impor- 

 tance of eliminating as many species as possible from the 

 genus Melania, which is so enormously extended as almost to 

 prevent the possibility of finding suitable names for the species. 

 In the Proceedings of the Academy, Dec, 1861, I stated that 

 Prof. Haldeman's genus Lithasia formed a very excellent 

 group. In working up a very large number of the familv 

 Melanido', obtained from the Southern and Western States, I 

 have, notwithstanding the divisions which had been made, 

 found myself embarrassed with that form of aperture which is 

 quite different from the auger-mouthed [Trypanosioma) species 

 and the Lithasia, to whicli latter they are most nearly allied. 

 I mean tliose which usually, though not always, have a slight 

 thickening of the upper part of the columella and no callus 

 below, and which are also without the notch of Lithasia, 

 although subangular at base. In this subangular character 

 they differ from 31elania proper, which are round or loop-like 

 at the base. For this group I propose the name of Goniohasis,^ 

 which will give us for our American Melanidse the following 

 genera, all of them having spiral opercula : — 



" Melania,-[ Lam,, Anculosa, Say, lo, Lea, Lithasia, Hald., 

 .Schizo stoma, Lea, Strephohasis, Lea, Trypanostoma, Lea, Gonio- 

 bisis^ Lea, and Amnicola, Gould and Hald. 



* Adams' Elimia takes in part of this genus. 



I Cuvier describes Melania as having long tentaciila, the eyes being on 

 the exterior side about the third of the lengtli. Tlie eyes of Melania 

 Virginica, Say, are at the base of short tentacula. I very much doubt if 

 we have a single species in the United States properly belonging to this 

 genus, fwhich Cuvier considered amarula as the type, and Lamarck, 

 asperata as the type. 



