38 COLIMACEA. 



with tooth-like plaits, and a small spiral, clastic, shelly plate, 

 attached by an elastic pedicle to the columella teeth within ; 

 destitute of an operculum. 



The shelly bone which is attached to the columellar teeth is 

 termed the clausium, and from whence the generic name is 

 derived. Its function seems to be, to close up the aperture, 

 when the animal has receded within its shell. A highly dis- 

 tinctive character in the shells of this genus, is, that the body 

 is usually less in diameter, than the volution next it. 



Section I. — Shell smooth ; the clausium or shelly plate tcith 

 a notch at top, Jitting into a plait situated on the outer lijj of 

 the aperture. 



1. Clausilia bidens, pi. IV, f. 33, 34. 



Clausilia bidens, Drapernaud, Hist, des Moll., p. 60, pi. 4, f. 

 5,6,1; Pfciffer, p. 60, pi. 3, f. 25 ; Brard, p. 83, pi. 3, f. 9 ; 

 Alder, Mag. Zool. and Bot., II, p. 110; Rossmassler, Icon., I, 

 p. 76, pi. 2, f. 29 ; Fleming, Brit. An., p. 271 ; Thompson, 

 Ann. and Mag. Nat. Hist., VI, p. 42 ; Helix bidens, Miiller, 

 Verm., II, p. 116, No. 315; Turbo laminatiis, Montagu, Test. 

 Brit., p. 359, ph 11, f. 4 ; Clausilia lainellata. Leach, Moll., p. 

 118; Turton, Man., p. 70, f. 53; Bulimus bidens, Bruguiere, 

 Ency. Moth., p. 352, No. 93; Clausilia bidens, Brov\n, lUust. 

 Conch., p. 37, pi. 14, f. 12 ; lb.. First Ed., pi. 41, f. 12. 



Shell with from ten to twelve reversed, smooth, glossy, pel- 

 lucid volutions, of a reddish horn-colour ; body volution very 

 small ; spire very long ; the volutions thickening towards the 

 middle, and tapering from thence to a small, somewhat obtuse, 

 and rounded point; each of the volutions swelling a little in 

 the centre, and the whole well defined by the suture line ; 

 aperture suborbicular, compressed, thickened, and white at the 

 upper outer margin, where it unites with the body ; outer lip 

 white, slightly marginated and rcflexed, with two laminar plaits 

 or folds, one of which is straight, situate near the superior 

 portion of the aperture, and nearly central, the other somewhat 

 curved, placed in the middle of the pillar lip, and frequently 

 crenated; deep within the aperture are situate three or four pro- 

 minent ridges, which are discernible when held up betwixt the 

 observer and the light. General length three-quarters of an inch ; 

 diameter, one-fourth of its length: the clausium is cmarginate. 



