LITUACEA. 177 



conical, with whorls somewhat rounded ; the last being larger 

 than all the rest together ; with the apex pointed, longitudinally 

 grooved; aperture oval, larger anteriorly than posteriorly, with 

 the lips disunited, the right lip simple, separated from the left 

 by a rather indistinct notch, or a slight emargination in the 

 contour. The left lip slightly reflected backwards, so as to form 

 a kind of salient margin with the anterior extremity of the 

 columella, which is united, rounded, arcuated and slightly 

 truncated at the anterior." — Obs. The Molluscous animals, whose 

 shells are thus described, are found in the Mediterranean , and 

 are remarkable for the power of suspending themselves from 

 the sea- weed on which they live, by a thread resembling a spider's 

 web. The general appearance of the shell presents a medium 

 between Phasianella and Littorina, but it is apparently destitute 

 of an operculum. 



LITTORINA. Fer. (Littus, the sea-shore.) Fam. Turbinacea, 

 Lam. — Bescr. Turbinated, thick ; spire acuminated, consisting 

 of few whorls, about one third of the axis in length ; aperture 

 entire, large, rounded anteriorly; outer lip thickened within, 

 acute ; columella rather flattened ; operculum horny, spiral, with 

 rapidly increasing volutions. — Obs. The shells composing this 

 genus are known from Turbo and Phasianella by the horny 

 operculum ; and from Trochus, which has also a horny opercu- 

 lum, by the small number of the whorls. The Littorinse, among 

 which may be enumerated the common Periwinkle, are, as the 

 name implies, found on sea shores, feeding upon seaweed, in all 

 parts of the world. Fig. 363, L. Vulgaris. 



LITUACEA. Bl. The second family of Polythalamacea. Bl. The 

 shells are described as chambered, symmetrical, convolute in part 

 of their extent, but constantly straight towards the termination. 

 The genus Spirula, which is admitted into this family, does not 

 properly belong to it, any more than to the Lituolae of Lamarck, 

 in which it is also placed. It does not agree with the descriptions 

 of either. This family partly corresponds with the " Lituolees," 



N 



