OF CONCHOLOGY. 119 



" They may be known by, 



" Melania having a regular loop-form aperture. 



"■ Anculosi having a rounded aperture and a callous columella. 



" lo 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. 



'^ Strephohasis having a retrorse callus at base, and usually a 

 squarish aperture. 



" Trypanostoma having an expanded outer lip and an auger- 

 shaped aperture. 



" GoniohasishnY iwg usually a subrhomboidal aperture, suban- 

 gular at base and without a channel. 



'^ Amnicola" having a round mouth and no callus." 



In Proc. Academy of Nat. Sciences, Jany., 18(34, Mr. Lea 

 proposed the following : — 



^' Mesechiza. — Shell fusiform, imperforate. Aperture rhom- 

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

 Columella smooth, incurved. Operculum corneous, spiral. 



" The little shell which I now propose as a new genus, lias so 

 distinct a character in the incision of the middle of the outer 

 lip, as to mark perfectly its place in the 31elani dae oHhe United 

 States. It differs entirely in the character of the cut from that 

 in Schizostom'i, which has, in all the many species I have seen, 

 a more or less deep incision immediately under the suture. 

 The living soft parts have not yet been observed. They may, 

 when examined, prove to have some characteristics quite dif- 

 ferent from Schizostoma.''^ 



Eurycselon. — In remarks on Goniohasis umbonata, (Proc. 

 Acad., p. 3, Jan. 1864,) " This is the fourth species of a natural 

 group which I have described and which have a large ear- 

 shaped aperture. If they be not entitled to a generic place, 

 they may at least be considered a subgenus, for which I pro- 

 pose the name oi Eun-ycselon, the aperture being larger than in 

 the 3felxnkloe generally. All the species of Eurycselon have a 

 callus on the columella above, but not below, as in Lithasia, 

 and the base is more or less angular, which is not the case with 

 Ancuhsa. Those which we have considered as varieties of 

 Anculos a ])r serosa, Say, which have an angular base, properly 

 belong, I think, to Eurycselon, as well also Anthoiiyi, Redlield, 

 turbinitr, and iintinnabu'Ium (nohis,) and some others. When 

 the soft parts shall be examined, they will, I think, be found 

 to differ from Goniohasis, Trypanostoma and Lithasia, to which 



* Jimnkola, although much Hke Paludina, is more nearly allied to the 

 Mclanida;. The operculuni is spiral, and, therefore, very different in this 

 character from Paludina. 



