MALACOZOA. GASTEROPODA. PULMOBRANCHIATA. 103 



the outer lip. The bipartite tooth then is not characteristic 

 of Clausilia dubia, which differs only in being more fusiform. 



The clausilium is curved, thin, with a thick revolute smooth 

 margin. 



The animal is very slender and elongated. "When it is in 

 motion, the foot is compressed, linear-oblong beneath, about 

 a third of the length of the shell, pale grey, semitransparent ; 

 the neck semicylindrical, striato-sulcate, transversely rugose, 

 dusky grey ; the upper tentacula short, nearly cylindrical, with 

 a large terminal knob, and black ; the lower very short, form- 

 ing two cylindrical knobs, and of a lighter tint. The shell is 

 dragged in the same line as the foot and neck, the animal 

 being incapable of raising it, unless when about to repose, 

 when it inclines at an angle of about 70°. 



First found by me, on the 18th of June, 1842, among wet 

 moss by a spring in Thorny-hive near Stonehaven ; next on 

 the 6th of August, under stones and turfs, by a mill in a creek 

 near Slains Castle, and in a Cove near the Bullers of Buchan, 

 where it is abimdant ; in September, by Miss Macgillivray, in 

 the Den of Auchmedden, at the Old Castle of King Edward, 

 in Aberdeenshire, and at Gamrie, in Banffshire, in great pro- 

 fusion. 



Helix perversa. Muller, Verm. Terr, et Aquat. ii. 118. — Turbo 

 nigricans. Dillu. Cat. 375. — Turbo perversus. Perm. Brit. Zool. 

 Ed. n. iv. 311. PI. 85. f. 3.— Turbo bidens. Mont. Test. Brit. 

 357. PI. 11. f. 7. — Clausilia perversa. Flein. Brit. Anim. 271. — 

 Clausilia rugosa. Lamk. Ed. n. viii. 201. — Clausilia rugosa. 

 Drap. Moll. 73. PI. 4. f. 19, 20.— Clausilia nigricans. Gray's 

 Turton, 217. PI. 5. f. 58. 



Clausilia dubia scarcely deserves being adduced even as a 

 variety. Its description, taken from specimens found in 

 various places, is as follows : — 



Shell slender, turrito-fusiform, glossy, semitransparent, with 

 about twelve little convex, transversely sulcato-striate, dis- 

 tinctly separated turns, the first two shining, smooth, forming 

 an obtuse apex, the rest gradually enlarging to the penulti- 

 mate, the last three faintly striate spirally, the ultimate nar- 

 rowed, with two wide grooves or undulations ; the aperture 

 subovate, narrowed near the posterior end, with the margin 

 thick, continuous, reflexed ; the columella with two plaits, of 

 which the anterior is forked internally ; the colour deep red- 

 dish-brown, with silky lustre ; toward the margin of most of 

 the whorls small grey indistinct spots at intervals formed 



