138 MALACOZOA. GASTEROPODA. PECTINIBRANCHIATA. 



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

 Johnst. Berw. Tr. 1835. 268. Turbo jugosus. Mont. Test. Brit. 586. 



3. Littorina saxatilis. Hock Periwinkle. 



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

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

 obtuse ; the whorls 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 eolour. 



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 



