COLIMACEA. 37 



perversa, Fleming, Brit. An., p. 271 ; Bala;a perversa, Thomp- 

 son, Ann. and Mag. Nat. Hist., VI, p. 41 ; Odoslomia perversa, 

 Fleming, Edin. Ency., VII, p. 76 ; Clausilia fragilis, Jeffreys, 

 Linn. Tr., XVI, p. 351; Pupa fragilis, Drapcrnaud, Hist, des 

 Moll., p. 68, pi. 4, f. 4 ; Turbo perversus, Montagu, Test. Brit., 

 p. 355, pi. 11, f. 12; Maton and Racket, Linn. Tr., VIII, p. 

 181, pi. 5, f. 2; Brown, Ency. Brit., 6th Ed., VI, p. 456; 

 JBalcea fragilis, Brown, Illust. Conch., p. 37, pi. 14, f. 11; lb., 

 First Ed., pi. 41, f. 11. 



Shell elongated, subpellucid, thin, with a yellowish-brown 

 epidermis ; body short ; spire very long, consisting of from five 

 to eight somewhat ventricose volutions, well defined by the 

 suture, and terminating in a slightly obtuse apex; aperture 

 subquadrate ; outer lip thin, white, a little reflected ; pillar lip 

 white, narrowly reflected on the columella, with a small sub- 

 umbilicus behind; whole shell covered with slender longitudinal 

 striae. Length seldom exceeding a quarter of an inch ; dia- 

 meter a fourth of its length. 



Old shells are frequently furnished with an obsolete tooth- 

 like fold about the middle of the columella. 



This species has much the aspect of a Clausilia, and may be 

 mistaken for a young shell of that genus, but is distinguished 

 by the body being convex and simple, and destitute of the 

 carinated ridge near the outer edge, as in the young Clausilice. 

 The volutions being sinistral, will at once mark it from the 

 genera Pupa and Bulimus. 



This is a very local species, in Britain, inhabiting the trunks 

 of trees, under the loose bark, or lurking in the Lichens which 

 invest the bark ; and is not unfrequently met with in the clefts 

 of rocks. According to Thompson, it is generally distributed 

 over Ireland. 



Genus XVIL—CLAUSILIA.— Drapernaud. 



Shell sinistral, elongated, fusiform, turreted, slender; spire 

 with numerous volutions, terminating in a somewhat obtuse, or 

 papillary apex, and swelling gradually towards the body — some 

 species are thickest in the centre ; aperture ovate, irregular, 

 oblique, peretreme, continuous, united all round, the lip gene- 

 rally thickened on the edge, and reflected ; columella furnished 



