14 DESCRIPTION OF 
Patupina 'TROOSTIANA. 
Testa ventricoso-conoided, tenut, pellucida, luteo-corned, levi, perforata; spird brevi; suturis valdé impressis; an- 
Sractibus quaternis, convemis; apertura magna, rotundatd, alba. 
Shell ventricoso-conical, thin, pellucid, yellowish horn colour, smooth, perforate; spire short; sutures very much im- 
pressed; whorls four, convex; aperture large, rounded, white. 
Hab. Tennessee. Prof. Troost. My Cabinet, and Cabinet of Prof. Troost. Diam. .68, Length .72 
of an inch, 
Remarks.—This is a subglobose species, differing from any which has come under my 
notice, in having the superior portion of the last whorl somewhat flattened, giving the 
shell a somewhat gibbous appearance. ‘The operculum is rather of a light colour, and the 
plane of the aperture is very retuse atits base. It has a strong resemblance to P. wnicolor, 
(Lamarck, ) and perhaps a stronger one to P. Maheyana, (Grateloup.) It is more depressed 
in the spire than either, and the perforation is smaller than in the former, while it is near- 
ly the size of that in the latter. The aperture is larger than either. Dr. Grateloup has 
very properly, I think, separated the Malabar species from that which was observed by 
Olivier in Egypt, and called wnicolor by Lamarck. The Egyptian shell has a larger per- 
foration, is darker in colour, and is alarger species. I call this after my friend Prof. Troost. 
GENUS ANCULOSA. (Say.) 
The genus Anculosa was proposed by Mr. Say, in the Journal of the Academy of Na- 
tural Sciences, vol. 2, p. 178, (1821,) for a new shell, which he then described under the 
name of Melania prerosa. I am not aware that he ever published a description of his pro- 
posed genus, but he then mentioned, that it did not correspond with the genus to which 
he “at present referred it,” and he farther says, that “owing to the configuration of the 
base of the columella, if it is not a Melanopsis, it is probable its station will be between 
the genera Melania and Achatina.” 
Four years afterwards, in describing a new species of the same group, under the name 
of Melania subglobosa, he says, “It is a second species of my proposed genus Anculotus.”’ 
He does not allude to the fact of having changed the termination of the name of his pro- 
posed genus. I have, therefore, always made use of the first, believing that the change 
was made through inadvertence. Mr. Haldeman, in his ‘‘Monograph of the Limniades,”’ 
very properly uses Anculosa, while Mr. Conrad, in his “New Fresh Water Shells,” with 
some other zoologists, uses Anculotus. 
The generic characters of the shell of this animal, are difficult in some cases to seize, as 
the form of the aperture varies, as well as the form of the spire, (notwithstanding its name, ) 
in many species. 
Mr. Haldeman seems first to have observed the animal, which he found to differ from 
Melania. He describes it, as having a “very small foot, adapted for holding; animal se- 
dentary ; inhabits very rapid water, attached to stones.” This of course separates it from 
Melania, and the “obvious characters” of the shell will generally distinguish it from both 
Melania and Paludina, as it has usually a callous columella, and a rounded aperture, 
The operculum, like that of Melama, is subspiral; at the same time it appears to me, that 
the point of radiation in that of Anculosa is usually nearer the margin. In the older 
specimens, the point of radiation is often directly on the margin, This, probably, is 
owing to part of it being worn away by the motion of the animal. 
