LECTURES ON MOLLUSC A. 215 



horny operculum ornamented outside with spiral dottings of shelly 

 matter. The mouth always ends in a round varix. They are sepa- 

 rated under the name Liotia. 



There is a group of very beautiful little white shells, with flattened 

 spire and large mouth, the relations of which are not yet properly 

 ascertained. As far as the shells are concerned, they pass both into 

 Liotia and liotella by insensible gradations. The shells are not pearly 

 as in the Trochids. The species are very numerous in west tropical 

 America, and probably in other warm seas, but have hitherto escaped 

 observation. They are here provisionally classed with liotella simply 

 from the relations of the shell. 



Family RotellidjE. 



The shell of liotella is like a marine Helicina, flattened, with a large 

 lump on the pillar. It is glossy, but not pearly. The operculum is 

 horny and many-whirled. The animal is said to have a retractile 

 proboscis. At any rate it offers the anomaly of having only one of the 

 eyes properly developed. One of the tentacles is curiously transformed 

 into along veil, which has been mistaken for a breathing pipe. The 

 creature is said to grub in sand, like the Naticas. The shells are 

 beautifully painted, with such variety of pattern that it is hard to find 

 two alike. Several allied forms are found in the secondary rocks. 

 Ghrysostoma takes the form of the Periwinkles, with a very small lump. 

 Camitia is toothed, like a polished Clanculus. Isanda has an open 

 pillar, with 'a toothed mouth. Teinostoma is like a liotella, with the 

 mouth drawn away from the pillar, and often ending in a pinch. 

 Elhalia is intermediate between the three last forms ; having an open 

 pillar nearly covered by the revolving lump of the inner lip. In Vitri- 

 nella there is no lump ; the pillar is extremely wide and open; and the 

 outer lip is often waved. The shells are all minute ; and are remark- 

 able for the large size of the nucleus and the beauty of the sculpture. 

 Cyclostrema is like a large Vitrinella, with a round mouth; it is said 

 to have a shelly operculum. Lastly, Adeorhis has a very open mouth, 

 with the outer lip doubly waved. In form, this group passes into the 

 next family. 



Family Stomatid^e. 



These may be described as Ear-shells without any holes. The animals 

 are like those of Haliotis, but without the mantle-slit. Like them the 

 mantle is fringed, but there are no feelers round, as in the Trochids. 

 They pass into the former family though the genus Stomatclla, in 

 which the shell is shaped like Sigaretus, and the animal can be drawn 

 into it. There is a small, horny operculum of few whirls. The shells 

 in the whole family are brilliantly pearly ; they are small, and almost 

 confined to the East Indian islands. In Slomatia, and the remaining 

 genera of the family, there is no operculum, and the animal cannot 

 withdraw its large foot into its shell. Sometimes, when frightened or 

 angry, it throws off the back of the foot, like the Harps. In Microtis, 

 which has a flat, spiral shell exactly like an unbored Haliotis, the foot 

 is cleft in front below the head. In Gena, the shell is drawn out, and 



