136 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



considerably from it in form, such as Turbo neritoides ; 

 and were mere outline to be assumed as indicating generic 

 difference, we might form of them two or three genera ; 

 but it seems expedient to leave them together. Several 

 of the most recent authors still refer the species here 

 described to the genus Turbo. 



Animal with the body elongated, spiral ; mouth with 

 two triangular thick lips, and a spiral ribbon-like tongue, 

 marked with numerous transverse denticulate striae ; two 

 tapering, depressed, obtuse, contractile tentacula, bear- 

 ing the eyes near their base, which is dilated ; foot oval, 

 short; operculum ovate, horny or calcareous, spirally 

 marked. 



Shell ovoidal, ovato-conical, or subglobose ; with the 

 spire short, the whorls convex, longitudinally striate, the 

 last very large, ventricose ; the aperture roundish, the 

 peristome incomplete behind, the pillar-lip thickened 

 and generally covering the umbilicus, the outer lip 

 thick, bevelled to a thin edge. 



They feed on vegetable substances ; adhere to rocks, 

 stones, and other hard bodies, or to plants, and move 

 about with ease, creeping in the manner of snails. The 

 species, being generally not confined to particular kinds 

 of situation, vary much in appearance. 



1. Littorina littorea. Common Periwinkle. 



Shell subovato- conical, thick ; with the spire half the length 

 of the last whorl, the apex acute ; the whorls convex, longi- 

 tudinally striate ; the suture distinct but very small ; the 

 mouth roundish ; the peristome very thick, bevelled to a thin 

 edge, the outer lip forming an acute angle at its junction, the 

 inner thickened by callosity ; the exterior dusky, with irregular 

 greyish or whitish longitudinal lines or bands ; the interior 

 dusky grey, the inner thickened part of the peristome white, 

 its thin margin dusky with light-coloured lines. Length, an 

 inch and a quarter, breadth three-fourths of an inch. 



Animal with the head and tentacula black or spotted ; the 

 foot whitish, yellowish, or grey, ovato-elliptical, transversely 

 rugous, with a medial depressed line, and crenate margins ; 

 the neck grey ; the thin margin of the mantle yellowish-grey. 



