218 NEW MELANIDiE OF THE UNITED STATES. 



different from the auger- mouthed {Trypanostoma) species and the Lithasia, to which 

 latter they are most nearly allied. I mean those 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 Melania proper, which are round or loop-like at 

 the base. For this group I propose the name of Goniobasis* which will give us for 

 our American Melanidce the following genera, all of them having spiral opercula : 



Melania,'\ Lam., Anculosa, Say, Io, Lea, Lithasia, Halcl., Schizostoma, Lea, Strepho- 

 basis, Lea, Trypanostoma, Lea, Goniobasis, Lea, and Amnicola, Gould and Hald. 



They may be known by, 



Melania having a regular loop-form aperture. 



Anculosa having a rounded aperture and a callous columella. 



Io having a greater or lesser elongate channel or spout at the base. 



Lithasia having 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 usually a squarish aperture. 



Trypanostoma having an expanded outer lip and an auger-shaped aperture. 



Goniobasis having usually a subrhomboidal aperture, subangular at base and with- 

 out a channel. 



Amnicola% having a round mouth and no callus. 



Goniobasis Hartmanii. PI. 34, fig. 1. 



Testa laevi, conica, magna, vel tenebroso-cornea vel tenebroso-oliva, valde vittata, imperforate ; spira 

 obtuse conica; suturis valde impressis ; anfractibus subplanulatis, instar septenis, ultimo grandi; 

 apertura grandi, ovato-rhomboidea., intus brunneo-vittata, ad basim obtuse angulata; labro acuto; 

 columella ineurvata. 



Shell smooth, conical, large, dark horn or olive color, much banded, imperforate ; 

 spire obtusely conical ; sutures much impressed ; whorls somewhat flattened, about 

 seven, the last large; aperture large, ovately rhomboid, brown, banded within, ob- 

 tusely angular at the base ; outer lip sharp ; columella incurved. 



Operculum ovate, spiral, dark brown, rather rough, with the polar point on the 

 edge, about J from the base. 



Melania Hartmaniana , Proc. Acad. Nat. Sci., 1861, p. 117. 



* Adams' FAimia takes in part of this genus. 



f Cuvier describes Melania as having long tentacula, the eyes being on the exterior side about the third of 

 the length. 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 this genus, which Cuvier considered 

 amarula as the type, and Lamarck, asperata as the type. 



X Amnicola, although much like Paludina, is more nearly allied to the Melanidce. The operculum is spiral 

 and therefore very different in this character from Paludina. 



