Species of the genus Truricatella. 303 



Hab. Var. /3 infra lapides in littore septentrionali Insulae Maderae; 

 V. V. — a et j3 in littore Maris Mediterraneae, Draparnaud, Lamarck, et 

 Payraudeau, loc. cit. — v. m. e Museo Dni. Sowerby. 



2. Truncatella Clathrus, Nob. 

 Trunc. testa subpellucidd, solidd, pallide corneo-lutescente ; anfractibus 



costis magnis raris csquidistaniibus elevatis transversis sculptis, per 



totam testa longitudinem decurrentibus. 



Longit, 2 lin.; lat. 1. Anfr. 4. 



Hab. > E Museo araici et eel. G. B. iSowerby. 



3? Truncatella Montagui, nob. 

 Trunc. testa tenui angustd, lineari, spird obtusissimd apice abrupid 



quasi truncatd ; suturd distinctissimd, valde coarctatd. 



Long. If, lin.; lat. | lin. Anfr. 4i. 



Turbo truncatus, Mont.,Test. Brit., " pi. 10, f. 7." Turt., Diet. no. 65. 



Jestajunior? 



Turbo subtruncatus, Mont., " pi. 10, f. 1." Turt. Diet. no. 64. 



Hab. in littore Britannico, v. m. 



The young shells in this genus difter so remarkably in form from the 

 adult, that they have occasionally been described as distinct species. One 

 of the species, (adult), is placed by Lamarck among his Cyclostomata, 

 though it is but fair to add as a doubtful species. Yet there can be no 

 doubt, if it belong to any of his genera, it should be placed in Paludina; 

 whither in fact Payraudeau has properly removed it. Indeed it is to 

 Litlorina that Truncatella bears the greatest affinity in the structure of 

 its animal. Yet the very peculiar modification of this structure, joined 

 to the singular habit, mode of crawHng, &c. is surely sufficient to 

 distinguish them. Added to this, the shells differ in their cylindric decol- 

 lated or truncated spire, and transversely striated and sculptured (or at 

 least with a tendency to be so) volutions. The same characters, with the 

 additional one of the absence of lateral membranes on the body of the 

 animal, and the want of an epidermis to the shell, distinguish them from 

 the true fluviatile Paludina. And the rounded shape of tlie foot and 

 proboscidiform muzzle essentially separate them from Rissoa: in which at 

 present imperfectly defined genus, all the species which have come under 



