I/O HE Lie I DAL. 



Shell sinistral, fusiform, or clavate ; month pear-shaped, or 

 oval, deeply grooved above, furnished with plaits or folds as 

 well as teeth, there is also within the throat or cavity, and distant 

 about half a whorl from the aperture, a spiral shelly plate 

 {clausium) which is attached by an elastic stalk to the pillar 

 and closes the aperture of the shell when the animal retires 

 within it ; outer lip continuous, body whorl furnished at its base 

 with a ridge or basal crest; uinbilictis very small. 



The ClausilicE are closely allied to the Bulivti and 

 Pupce. They are vegetable feeders, and it is probable 

 that all the British species are viviparous, Mr. Rich 

 having noticed that this is the case with three of 

 them, viz. C. rttgosa, C. Rolphii, and C. biplicata. 



The claiLsmm with which these animals are provided 

 as a protection against the inroads of their enemies 

 forms the most remarkable characteristic of the genus. 

 Dr. Gray, in 'The Zoological Journal,' vol. i. p. 212, 

 thus aptly describes it : " Of all the wonderful con- 

 trivances employed by Nature for the protection of 

 the mollusca, there is none which is more calculated 

 to excite the admiration of the conchologist than the 

 clausmm — an elastic appendage which closes the aper- 

 ture of the Clausiliae. It consists of a spirally-twisted, 

 thin, shelly plate, enclosed in the last whorl of the 

 shell, and attached to the columella by an elastic 

 pedicle. When the animal is retracted within its 

 shell, this shelly plate nearly covers the aperture at a 

 little distance within the mouth, and coming in con- 

 tact with a transverse plait on the outer lip, leaves 

 only a small canal, formed between the outer plait 

 and the posterior angle of the mouth, and some- 

 times an elongated longitudinal plait on the inner lip. 

 When the animal wishes to protrude itself it pushes 



