DESCRIPTION OF A NEW GENUS (BASISTOMA,) OF THE FAMILY MELANIANA, 
TOGETHER WITH 
SOME NEW SPECIES OF AMERICAN MELANI®. 
FAMILY MELANIANA. 
GENUS BASISTOMA.* 
Testa conica. Apertura ovata, basi abscissa. Labrumacutum. Columella levi. Operculum ——. 
Tue particular shell for which I propose this genus was given to me by Amory 
Edwards, Esq., late the Consul of the United States at Rio, who brought it from four 
hundred miles up the river Tocatinus, five hundred miles distant from the ocean, at the 
mouth of the Amazon. It differs from any of the family of Melaniana in the cut at the 
base, and it has none at the superior part of the aperture. It comes near to Pirena, but 
wants the superior cut, and it differs from Melanopsis in its general form as well as in 
having no callus on the columella. The Melaniana being so enormously developed, and 
having but few genera, I think it advisable to constitute new ones, whenever a group can 
be well characterized, which is the case with this form. I think that Melania transversa, 
(Nobis,) from Guiana, and M. Braziliensis, (Nobis,) would properly come under this 
division, and very likely other characteristic species will be found in that portion of South 
America whence these three come. The genus Melatoma, Swainson, is a well charac- 
terized group in some respects near to this. While it is emarginate at base, it has an 
emargination also towards the upper portion of the outer lip, and the group, as far as I 
know it, has a general and well characterized outline, being somewhat mitraform. I 
think that my M. microstoma, tornatella and rudis all belong to a group which would con- 
stitute a new genus, unless it could be put into one of Mr. Swainson’s genera, all the 
types of which I have not seen. 
* Baots, base, and reuva, to cut. 
When I proposed the name of Schizostoma for a genus of Melaniana with a cut at the superior portion of 
the aperture, I was not aware that M. Bronn had already used that name for a fossil genus. I now propose to 
substitute Schizochilus, from oxo, to cut, and ysiaos, lip. 
