DESCRIPTION OF A NEW GENUS (BASISTOMA,) OF THE FAMILY MELANIANA, 



TOGETHER WITH 



SOME NEW SPECIES OF AMERICAN MELANI^E. 



FAMILY MELANIANA. 



GENUS BASISTOMA.* 



Testa conica. ^ertura ovata, basi abscissa. Labrum acutum. Columella Issvi. Operculum . 



The 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 Melaioma, 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. Svvainson's genera, all the 

 types of which I have not seen. 



* /3a(rt{, base, and •t't/tnj, to cut. 



When I proposed the name of Schizostomu for a genus of Melaniana with a cut at the superior portion of 

 the aperture, I was not aware that M. Bronn liad already used that name for a fossil genus. I now propose to 

 substitute Schizochilus, from nxti^a, to nit, and ;{">■''«> Hp- 



