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Shell Life 



form, the mouth narrowed, and often further reduced 

 by tooth-like growths. The genus Bidmiinus, which 

 has but two British representatives, agrees generally 

 with Helix, but the tentacles of the animals are shorter, 

 and the character of the lingual teeth is different, the 

 rows being curved towards the margins. The Moun- 

 tain Bulin (B. onontanus) has a semi-transparent shell 

 about two-thirds of an inch long, slightly 

 glossy, and of a pale brown tint. The surface 

 is crossed by delicate spiral and transverse 

 lines, the crossing of which gives the shell the 

 appearance of being minutely shagreened. 

 There are seven and a half whorls, the body- 

 whorl accounting for one-half the shell. The 

 oval mouth, which has a white lip, is reddish within. 

 It is found on the trunks of ash, beech, and hornbeam, 

 in Somerset, Oxfordshire, Gloucestershire, and Suffolk 

 only. The Lesser Bulin (B. ohscwrus) is very like it, but 

 smaller — a little more than one-third of an inch long. 

 It is further distinguished from the very similar 

 montaniis by being more glossy, the absence of spiral 

 lines preventing the shagreened appearance of its con- 

 gener; there are only six and a half whorls, 

 the lip is not so thick, the inside of the mouth 

 is white, and the body-whorl is only equal to 

 two-fifths of the whole. It is an inactive 

 creature, sticking on the bark of trees (beech 

 chiefly), apparently feeding upon the immature mosses 

 and lichens that grow thereon, and disguising itself 

 so that snail-hunting birds may pass it as a bit of 

 dirt or one of the small knots that are so common 

 on beech bark. It does this by covering its shell 

 with slime and dragging it across dirt of various 



