240 SNAILS AND SLUGS [CH. VII 



genus Vitrea, Fitzinger, shell orbicular, depressed, thin, whorls 

 increasing regularly, aperture oblique, umbilicus more or 

 less distinct. Animal capable of retreating entirely within 

 shell. Most occur under stories or wood in damp places, wet 

 moss ; avoid the light. 



lucida (Drap.), |", whorls 6 or 7, transversely striated, fawn 

 above, bluish-white below ; aperture oval, very oblique, um- 

 bilicus wide ; animal cobalt blue. 



pura (Alder), ^Q", whorls 4, last = half of shell; striae circular, 

 umbilicus narrow, deep. 



radiatula (Alder), |", whorls 4 or 4^, striae from whorl to whorl 

 not interrupted by sutures ; aperture semilunar, oblique ; 

 umbilicus moderately deep. 



nitidula (Drap.), f", whorls 4 or 5 ; striae interrupted by sutures ; 

 spire slightly produced ; aperture oblique, small. 



crystallina (Mull.), ^", whorls 4^ to 5, body whorl same as pre- 

 ceding whorl, aperture crescentic ; umbilicus small. 



alliaria (Miller), |", whorls 5, last moderately large, exposing 

 second whorl ; aperture semilunar, narrow. 



rogersi B. B. Woodward, |", whorls 5 or 5J, body whorl occupying 

 half of shell ; shell thin, glossy, compressed, transversely 

 striated, dark horn-coloured ; aperture | of a circle ; um- 

 bilicus narrow, deep. 



cellaria (MiilL), 3", whorls 5 or 6, last large ; shell pale horn. 



genus, Zonitodes Lehm., shell striated above, whorls increasing 

 gradually. 



nitidus (MiilL), ", whorls 5, shell sub-globose and brownish, aper- 

 ture oblique and roundish ; umbilicus narrow and deep. 



excavatus (Bean), J", whorls 5 ; shell thin, horn-coloured ; aper- 

 ture small, crescentic, umbilicus large, disclosing all the whorls. 



genus Euconulus Reinh., shell thin, perforate. 



fulvus (Miill.), ^j", whorls 5| or 6 ; shell keeled, conical, coloured, 

 aperture crescentic, umbilicus large, exposing second whorl. 

 In vaults and wells. 



Family HELICID^;. Animal terrestrial ; shell spiral, globose or coil- 

 shaped ; tentacles four, invaginable ; eyes at tip of upper longer 

 pair, 

 genus Helix L., shell globular or flattened, aperture circular or 



