FAMILY COLIMACEA. 45 



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Genus III. ZONITES, Be 



Animal ; rather slenderly elongated, bearing an umbilicated, nar- 

 row-whorled snbdiscoidal shell, of a semitransparent shining 

 horny substance, over which the mantle is a little reflected, 

 head with the upper pair of tentacles rather long, the lower 

 short, foot obliquely truncated posteriorly, minute palate teeth 

 aculeate. 

 Shell ; conspicuously umbilicated, depressly orbicidar, subdiscoidal, 

 semitransparent horny, shining, without spot or marking, spire 

 scarcely exserted, whorls three to five, narrow, rounded ; aper- 

 ture small, lip simple, margins widely removed. 

 The genus Zonites as lately restricted constitutes a very natural 

 group. The animal has a semitransparent shining horny shell, 

 composed of narrow discoidly convoluted whorls, of which the 

 lip is always thin and simple, and has the mantle reflected over 

 it somewhat after the manner of Vitrina. The posterior extremity 

 of the foot is more inclined to be truncated than it is in Helix, and 

 the minute palate teeth differ in being aculeate. The shell has no 

 epidermis ; it is deeply, sometimes largely, umbilicated, and there is 

 no encircling rib ^ within the aperture. 



Viewing the genus in a wider geographical range than Britain, 

 its characters, so far as they have been determined by naturalists, 

 are much less perfectly defined. M. Moquin-Tanclon refers four 

 distinct forms of Helicidce to Zonites, distinguishing them by the 

 sectional names Conulus, Calcarina, Aplostoma and Verticillus. 

 The British Zonites come into section Aplostoma, but he includes 

 with them the large Helix Algira and H. olivetorum of the Euro- 

 pean continent, whose shells are not of the same glossy substance 

 though presenting a considerable general resemblance in form and 



