Species of the genus Truncatella. 303 
Hab. Var. (3 infra lapides in littore septentrionali Insule Madere ; 
v. v.—a et 6 in littore Maris Mediterranee, Draparnaud, Lamarck, et 
Payraudeau, loc. cit.—v. m. e Museo Dni. Sowerby. 
2. TruncaTELLA CLatTuHRus, Nob. 
Trune. testd subpellucidd, solidd, pallidé corneo-lutescente; anfractibus 
costis magnis raris equidistantibus elevatis transversis sculptis, per 
totam teste longitudinem decurrentibus. 
Longit, 2 lin.; lat. 1. Anfr. 4. 
Hab. ————? E Museo amici et cel. G. B. Sowerby. 
3? TRUNCATELLA Montacut, nob. 
Trune. testd tenui angustd, lineari, spird obtusissimd apice abrupta 
quasi truncatd ; suturd distinctissimd, valde coarctatd. 
Long. 12, lin.; lat.2 lin. Anfr. 43. 
Turbo truncatus, Mont., Test. Brit., “ pl. 10, f. 7.” Turt., Dict. no. 65. 
Testa junior? 
Turbo subtruncatus, Mont., * pl. 10, f.1.’’ Turt. Dict. no. 64. 
Hab. in littore Britannico, v. m. 
The young shells in this genus differ 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 
Littorina 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 crawling, &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 
jeast 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 Paludine. And the rounded shape of the foot and 
proboscidiform muzzle essentially separate them from Réssoa: in which at 
present imperfectly defined genus, all the species which have come under 
