138 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA* 



Anim. 298. — Turbo rudis. Lamk. Syst. vii. 49. — Littorina rudis, 

 Johnst. Bern. Tr. 1835. 268.— Turbo jugosus. Mont. Test. Brit. 586. 



3. Littorina saxatilis. Rock Periwinkle. 



Shell subgloboso-conical, as broad as long, moderately thick ; 

 with the spire scarcely a third of the whole length, the apex 

 obtuse ; the whoi-ls three, longitudinally striate, the suture 

 distinct and deeply impressed, the last turn somewhat flattened 

 above, and angulate toward its lower part ; the mouth very 

 large, roundish, the peristome thin, the outer lip united at right 

 angles ; the exterior white, banded or tesselated with dusky, 

 brown, or green ; the interior deep chocolate-brown, the mar- 

 gin white or yellow, unless on the callosity of the inner lip, 

 where it is purplish-brown. Length four-twelfths of an inch, 

 breadth nearly the same. 



This species, very nearly allied to Littorina rudis, but appa- 

 rently distinct, varies little in form, but considerably in the 

 prominence of its spiral ridges, and greatly in colour. 



It first attracted my notice, as plentiful among Balani, on a 

 large block of gneiss, known as "the Black Deg," on the 

 sands of Belhelvie, about three miles north of Don-Mouth. 

 Abundant on the rocky coasts of Buchan and Kincardine, 

 about high-water mark, in crevices and among Balani. 



Turbo saxatilis. Bean. — Littorina saxatilis. Johnst. Berw. Tr. 

 iii. 268. 



4. Littorina tenebrosa. Marsh Periwinkle. 



Shell subovato-conical, rather thin ; with the spire as long as 

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

 tudinally striulate, transversely rugoso-striate ; the suture 

 distinct and deeply impressed ; the mouth roundish-oval, the 

 peristome thin, unless on the columella, the outer lip united at 

 right angles ; the exterior dusky, often banded or tesselated 

 with lighter tints ; the interior dark purplish-brown, the cal- 

 losity of the inner lip deep purple. Length nine-twelfths of 

 an inch, breadth from six to seven-twelfths. 



Animal with the head, tentacula, and collar black ; the foot 

 greyish, elliptical, transversely rugous, with a medial depres- 

 sion, and crenate margins. 



It varies in form, the last whorl being sometimes broader 

 than the length of the spire, sometimes equal to it ; in having 

 distinct or obsolete longitudinal lines ; and in colour, being 

 plain, or banded, or tesselated. It is always distinguishable 



