470 



Binney^s Monograph of the Helices 



transparent membrane; composed principally of hardened 

 gelatine w ith but little calcareous matter, stretched across 

 the aperture of the shell, never convex but sometimes a 

 little concave. The shell is hermetically sealed by this 

 covering, in which, after examination of nearly all our 

 species, I have not been able to discover the " extremely 

 minute orifice in the centre^ communicating loith an urn- 

 hilical chord of sufficient capacity for the passage of 

 oxygenated air necessary for the purposes of an extremely 

 . slow, but not totally extinct respiration" spoken of by 

 Mr. Turton.* On the contrary, I am fully convinced that 

 no such contrivance exists, and tliat the only air which 

 can serve the purposes of respiration during hybernation 

 is the small quantity contained in the shell at the moment 

 when the epiphragm. is formed. The destruction of the 

 epiphragm too, is ejSected in a more simple manner than 

 by the secretion of an acid to dissolve it, as supposed by 

 him ; it being easily broken down by the posterior part ol 

 the foot of the animal which is first protruded. 



The natural food of the genus is generally supposed to 

 be vegetable matter, and the formation of the mouth and 

 jaws seems to be peculiarly well adapted for cutting fruits 

 and the succulent leaves of plants. The dental edge of 

 the upper jaw, with its minute serratures, being apphed 

 against the substance to be eaten, the semilunar, sharp- 

 edged instrument which Spallanzani calls the tongue, is 

 brought up against it, cutting out and carrj'ing mto the 

 mouth semi-circular portions of the substance. xuis 

 operation is cai'ried on with great rapidity? and the suD- 

 stance to be eaten soon disappears. It is certain, how- 



Manual of the Land 



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