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 sVhs inch. Under the bark of old trees. Local. 



B. perversa.^ 



28. 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 ; clausilium 

 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. bide n tat a. ^ 



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

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

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

 prominent and sometimes cruciate j umbilicus indistinct ; clausilium 

 oblong. Length Jfths inch. Among dead leaves and under 

 the bark of tress. Rare. C. rolphii. 



(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 -J|-ths inch. On the bark 

 of willow trees. Very local. C. biplicata. 



88 v. viridula, greenish-white, transparent. 



89 v. gracilior, longer, more slender ; v. titmidula, smaller, shorter, more 

 ventricose ; v. everetti, shorter, whorls fewer ; v. suttoni, whorls eleven and 

 showing no striation ; v. cravenensis, whorls thirteen like var. suttoni but 

 strongly striated, and with a well-ma.rked palatal callus. 



