XXIX 



Prof. Haldeman's genus Litliasia formed a very excellent 

 group. In working up a very large number of the family Me- 

 lanidce, obtained from the Southern and Western States, I 

 have, notwithstanding the divisions which had been made, 

 found myself embarrassed with that form of aperture whicli is 

 quite different from the auger-mouthed ( Trypanostoma) species 

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

 I mean those which usualh', though not always, have a slight 

 thickening of tlie upper part of the columella and no callus 

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

 although subaugular at base. In this subaugular character 

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

 at the base. For this group I propose the name of Gonioba- 

 sis,* which will give us for our American Melanidcv, the fol- 

 lowing genera, all of them having opercula : — 



'■'Melania, t Lam., Anculosa, Say, lo, Lea, Lithasia^ Hald., 

 Schizostoma, Lea, Stre2:>hobasis, Lea, Trypanostoma^ Lea, Go- 

 niobasis. Lea, and Amnicola, Gould and Hald. 



" They may be known by, 



" Melania having a regular looi>form aperture. 



^'■Anculosa having a rounded aperture and a callous columella. 



" lo having a greater or lesser elongate <;hannel or spout at 

 the base. 



" Lithasiahsiymg a callus on the columella above and below, 

 and a notch at the base. 



" Schizostoma having a cut in the upper part of the outer lip. 



" Strephobasis having a retrorse callus at base, and usuall}' 

 a squarish aperture. 



" Trypanostoma having an expanded outer lip and an auger- 

 shaped aperture. 



" Goniobasi.^ having usually a subrhomboldal aperture, sub- 

 angular at base and without a channel. 



" Ajnnicolal having a round mouth and no callus." 



In Proc. Academy of Nat. Sciences, January, 1864, 

 Mr. Lea proposed the following : — 



" Meseschiza. — Shell fusiform, imperforate. Aperture rhom- 

 boidal, below canaliculate. Lip expanded, slit in the middle. 

 Columella smooth, incurved. Operculum corneous, spiral. 



* Adams' Elimia ttikos in part of this frenus. 



t Cuvier describes Mchtnin as having long tentacuUi, the eyes being 

 on the exterior side about the third of the lengtli. The 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 tliis gcnns, of which Ciivier considered amarula as the 

 type, and Lamarck, aspcrota as the type. 



t Amnicola, although nnicli like 'Falndina, is more nearly allied to 

 the JSManid<B. Tiic opercnliuH is spiral, and, therefore, very Uillerent 

 in this character from I'aiudina. 



