MALACOZOA. GASTEROPODA. PECTINIBRAXCHIATA. 137 



The shell varies in the degree of prominence of the longi- 

 tudinal ridges, in colour, and thickness. In young shells the 

 ridges are prominent and acute, in old individuals obsolete. 

 Young shells have the peristome thin without being bevelled, 

 the whole inside blackish-brown ; very old shells have the in- 

 side wholly white, others partly white. Frequently the surface 

 is corroded or crusted, so that the markings are obliterated. 



Occurs abundantly on all the rocky coasts ; also in estuaries 

 on stones. 



The animal affords an article of food, of little value, and not 

 much esteemed. In most seaport towns it is sold, chiefly to 

 the poorer people, who consider it a kind of luxury. 



Turbo littorcus. Linn. Svst. Nat. i. 1232. — Turbo littoreus. 

 Penn. Brit. Zool. iv. 128. PI. 81. f. 109.— Turbo littoreus. Flem. 

 Brit. Anim. 298.— Turbo littoreus. Mont. Test. Brit. 301.— Turbo 

 littoreus. Laruk. Syst. vii. 47. — Littorina littorea. Jobnst. iii. 267. 



2. Littorina riidis. Coarse Periwinkle. 



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

 of the last whorl, the apex acute ; the whorls very convex, 

 subangulate above, longitudinally striate, transversely rugoso- 

 striate ; the suture distinct and deeply impressed ; the mouth 

 oval, the peristome very thick, bevelled to a thin edge, the 

 outer lip united at right angles ; the exterior dusky, pale olive, 

 dull yellowish-grey, yellow, or red ; the interior purplish- 

 black, reddish-purple, yellow, or red. Length eight-twelfths, 

 breadth nearly seven-twelfths. 



Animal with the head, tentacula, and collar blackish-brown ; 

 the foot yellowish-grey, elliptical, transversely rugous. In 

 the red and yellow shells, the head and tentacula are brown, 

 the foot and mantle white. 



It varies considerably in form, the spire being shorter or 

 longer ; in thickness, being sometimes remarkably solid and 

 ponderous, sometimes thin and light; in its striae, which may 

 be obsolete, moderately developed, or very conspicuous ; in 

 colour, individuals being dusky, or brown, or light red, or 

 orange, or yellow, banded, or variegated. In almost all cases, 

 however, it may be recognised by the somewhat angular round- 

 ing of the upper part of the last spiral turn. The strongly 

 striate varieties have by some been considered as a distinct 

 species, named by Montagu Turbo jugosus. 



Abundant on all the rocky coasts, near high-water mark. 



Turbo rudis. Mont. Test. Brit. 304.— Turbo rudis. Flem. Brit. 



M 



