90 LAND AND FRESH-WATER SHELLS. 



sometimes with a denticle at the base of the penultimate whorl ; 

 peristome thin, umbilicus narrow. 



(a) Shell fusiform, turreted, glossy, yellowish horn-colour 

 streaked with white ; whorls seven to eight ; suture deepish ; 

 mouth rounded, pear-shaped, with sometimes a denticle near the 

 middle of the base of the penultimate whorl ; umbilicus small. 

 Height ^ths inch. Under the bark of old trees. Local. 



B. perversa.^^ 



23. Clausilia. — Shell sinistral, fusiform ; mouth pyriform or 

 elliptical, toothed, furnished with a clausilium ; umbilicus very 

 small. 



(a) Shell cylindrical, glossy, chocolate-brown or horn-coloured, 

 marked with whitish streaks ; whorls ten to thirteen ; mouth pyri- 

 form, furnished with two plications on the base of the penultimate 

 whorl with one to three smaller plaits between them, and with 

 two plications on the columella ; umbilicus narrow ; clausiHum 

 oblong. Height fths inch. Under stones, logs of wood, and 

 among grass on hedge-banks, on trunks of beech, willow, and ash 

 trees. Common. C. riigosa.^^ 



(b) Shell fusiform, reddish or yellowish-brown ; whorls nine to 

 ten, swollen ; mouth rounded, pyriform, with plaits as in C. ritgosa, 

 but the lower one on the base of the penultimate whorl is less 

 prominent and sometimes cruciate ; umbilicus indistinct ; clausilium 

 oblong. Length ^fths inch. Among dead leaves and under 

 the bark of tress. Rare. C. RolpJui. 



{c) Shell fusiform, yellowish-brown, streaked with white ; whorls 

 twelve to thirteen, compressed ; mouth pear-shaped, canaliculated, 

 with the same plaits as in the two foregoing species, except that 

 the teeth between the plications on the base of the penultimate 

 whorl are not represented ; umbilicus rather broad, basal crest 

 prominent , clausilium oval. Length ijths inch. On the bark 

 of willow trees. Very local. C. biplicata. 



^^ V. viridula^ greenish-white, transparent. 



^" V. diilna, larger, more ventricose ; v. gracilior, longer, more slender ; v. 

 iuniidula, smaller, shorter, more ventricose ; v. Everetli, shorter, whorls 

 fewer ; v. Schlechtii, like v. dubia but larger, elongated, smoother, and more 

 transparent, pale brown. (Possibly v. dubia is a distinct and separate 

 species.) 



