OF MOIXUSCA. 



101 



having a somewhat angular appearance on the longer outer or dorsal 

 outline. It is thick, strong, pale yellow, with about twenty-five 

 strong rounded ribs, broader anteriorly. Thus the septa of the shell 

 would appear to be thrice formed. — Stimpson, Shells N. Eng. 36, 

 1851. 



The apex of the shell of Ccecum, according to Dr. Shuttleworth, 

 is subspiral, the whorls being separated from each other, the tip 

 gradually falling off. One of the species described by Stimpson is 

 ovate, ventricose. 



When examining Mr. Bean's cabinet in 1850, I noted Vermicu- 

 laria incurva. It appears to be the young of Ccecum ; the apex is 

 spiral, the straight part is slightly transversely annulated. 



2. Brochina. 

 Operculum convex externally, with a succession of spiral terraces. 

 1. B. glabra. 



Operculum of Brochina glabra shaped like that of Siliquaria, of 

 five or seven coils rolled round a windlass, crenulated at the edges, 

 mammillated above and below, and on the summit are numerous 

 loeuli, like those in the centre of Polystomella. — Clark, Moll. 326. 



Mr. Clark considers the Ceecidce as very nearly allied, if not identical 

 with Vermetus ; that they are probably attached when young (?), and 

 at length become free, all other attached shells being free when first 

 hatched ; and lastly, that Skenea rota, which is free (!), is perhaps 

 the young of C. glabrum, — Moll. 325. 



Fam. XV. MELANIADjE. 



Gills in a single series of a moderate number of cylindrical rigid 

 plates. Mantle edge torn, with a more or less distinct siphon in 

 front. Rostrum produced, annulated. Tentacula subulate. Eyes on 

 the outer side of the base of the tentacles, sessile, or on short tuber- 

 cles. Shell spiral, turrited, covered with an olive periostraca ; aper- 

 ture ovate or circular. Operculum spiral. 



Fluviatile. 



a. Aperture of shell ovate, entire in front. 



1. Melania. 



Shell ovate or turrited ; spire acute ; mouth ovate, entire in front. 

 Operculum ovate, of few whorls. Rostrum wrinkled, elongate, 

 nicked. Tentacles filiform, with the eyes on the outer side of the 

 base. Foot moderate, ovate, rather square in front. Often vivi- 

 parous. 



1. M. amarula, t. 127 a. f. 6; (Tiara a.), Adams, Gen. Moll. 



t. 31. f. 3. 



2. M. setosa, t. 55. f. 2, 11. 



