186 
HELICID^. 
Animal grey. 
Shell an inch long, of a greyish brown horn-colour, 
tumid in the middle ; spire composed of ten or eleven 
rather swollen volutions, which are marked with re- 
gular raised longitudinal lines; aperture roundish- 
oval, sinuous at the upper and outer angle ; the 
margin thick, white, detached all round, with four 
or five plaits, two of which are much longer than the 
rest. 
Like other species, it is sometimes found transpa- 
rent and colourless. 
86. 4. Clausilia nigricans. Dark Close Shell. — 
Shell slender, sub-opaque, black-brown, with 
fine raised somewhat granular stride; aperture 
with three plaits, the margin white and detached 
all round, (t, 5. f. 58, 59.; t. 12. f. 143.) 
Turbo bidens. Montagu^ p. 357. t. 11. f. 7. (not Linn.') — 
Clausilia rugosa. Drap. p. 73. t. 4. f. 19, 20.; Leach., Syn. 
Moll. 87.—Turbo nigricans. Maton and Racket., Linn. Trans. 
viii. 180.; Mont. T. B. Supp. 131.; Dillw. 375.; Pult. Dor- 
set. AQ.'., Turt. Diet. 225 . — Odostomia nigricans. Flem. Ed. 
Ency. vii. 70. — Helix perversa. Muller ., Verm. 118. — Bu- 
limus perversus. Drug. — Turbo perversus. Penn. Brit. 
Zool. iv. t. 82. f. 116. ; Pulteney., Dorset. 46., part. — Clausilia 
nigricans. Jeffreys., Linn. Trans, xvi. 351. ; Gray., Man. 
217.; Forbes and Hanley., B.M. iv. 121. t, 129. f. 1, 2. — 
Clausilia roscida; C. cruciata. Studer, Schw. Conch. 20. — 
Clausilia perversa. Flem. B.A. 271. — Strombiformis per- 
versa, young. Da Costa., B, C. 187. — Clausilia rugosa, 
and C. obtusa. C. Pfeiffer., D. Moll. i. 63. 65. t. 3. f. 30. 
33, 34. 
Var 1., smaller, more slender (t. 5. f. 58.) : Clausilia parvula. 
Leach., MSS.., B. M. ; Turtom Zool. Journ. ii. 556., Man. 
ed. 1. 74. f. 58.; Jeffreys., Linn. Trans, xvi. 352. (not 
Sttider). 
