HELIX. 



185 



In this, the spire is more elevated, and sometimes has 

 six full volutions. There is a deep groove behind the 

 lip, contracting the aperture ; the lip is widely reflected, 

 and directed inwards, forming a basin-shaped mouth ; 

 the upper labial tooth is broader, sometimes bifid, and 

 even trifid, and very much inflected ; the columellar 

 tooth extends quite to the base of the shell, and unites 

 with the extremity of the lip ; the aperture is nearly 

 filled up by the teeth and the contraction of the lip. If 

 this variety were to be seen alone, it would be adjudged 

 to be a good species, and is generally so considered. 

 Having examined a great number of every variety, from 

 numerous localities, I have found every gradation be- 

 tween the extremes, and am convinced that they form but 

 one species. The animals do not differ in the least degree. 



Helix tridentata resembles Helix palliata on its upper 

 surface, but differs from all others. The situation in 

 which I have most commonly found it, is under the 

 layers of wet and decaying leaves in forests ; it is also 

 found under flat stones. I have one specimen in which 

 the direction of the whorls is reversed. 



The figure of Ferussac represents a very small shell, 

 probably the southern variety. Lister's figure, tab. 92 % 

 figure 92, is probably intended for this shell. 



VOL. it. 24 



