HELICID^. 



CLAIJSILIA. Draparnaud. 



Shell Spiral, produced, the last volution less turned than 

 the one before it, sinistral ; aperture pyriform, toothed ; 

 throat closed by an internal testaceous plate or clausium. 



Animal Short ; upper tentacles stout, lower ones very small. 



The great peculiarity in these shells is the clausium, 

 which is thus described by Gray. " It consists of a 

 spirally-twisted thin shelly plate, inclosed in the last 

 whorl of the shell. When the animal is retracted 

 within its shell, this shelly plate nearly covers the aper- 

 ture at a little distance within the mouth, and coming in 

 contact 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 sometimes an 

 elongated longitudinal plait on the inner lip. When 

 the animal wishes to protrude itself, it pushes the plate 

 on one side into a grove situated between the inner 

 plait and the columella, where it is detained by the 

 pressure of the body of the animal, leaving the aper- 

 ture free ; and when the animal withdraws itself, the 

 plate springs forward by the elasticity of the pedicle 

 and closes the aperture." 



C. LAMINATA. Montagu. PI. VI, fig. 27. 

 Shell large, nearly smooth, glossy, and serai-transparent. 

 Clausilia bidens, Gray., 8fc. 



This large Clausilia sometimes measures three quar- 

 ters of an inch in length. The shell is generally of a 

 brownish colour and smooth, except at the base of the 

 last whorl, which is slightly striated. Transparent 

 greenish white specimens are sometimes, though rarely, 

 to be met with. Whorls ten, slightly convex ; the 

 suture is distinct but not deep. The peristome thick 

 and whitish, not reflexed, of a pyriform shape ; the 

 upper plate is small and straight, the under one, which 

 is in the middle of the pillar lip, curved. The animal 

 brownish, the upper tentacles clavate. 



Hob. This shell is more common in the south than 



