LTTUACEA. 187 



conical, with whorls somewhat rounded ; the last being larger 

 than aU 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 sinus in the con- 

 tour. 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." — Ohs. 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 Kve, 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. 



LITTOElIsrA. Eerussac. {Littus, the sea-shore.) Fam. Tur- 

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

 consisting of a few whorls, about one-third of the axis in length ; 

 aperture entire, large, rounded anteriorly ; outer lip thickened 

 within, acute ; columella rather flattened ; operculum homy, 

 spiral, with rapidly increasing volutions. — Obs. The shells com- 

 posing this genus are known from Turbo and Phasianella by the 

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

 operculum, 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, feediag upon sea- weed, 

 in all parts of the world. L. Vulgaris. PI. xvi. fig. 363. 



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 termi- 

 nation. The genus Spirula, which is admitted into this family, 

 does not properly belong to it, any more than to the Lituolse of 

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

 descriptions of either. This family partly corresponds with the 

 " Lituolees," Lam. and contains the genera Lituola, Ichthyo. 

 sarcolites, Spirula, Hamites and Ammonoceras. 



