10 ZONTTID^). 



Animal elongate, completely retractile within the shell, having 

 a caudal mucus- pore, more or less developed, but consisting 

 usually of a simple linear slit ; mantle lobes small, not reflected 

 on the shell ; genital orifice distant from the right tentacle ; jaw 

 with a well-marked median rostrum ; lateral teeth bicuspidate, 

 marginals sharp, narrowly unicuspidate. 



Europe, Western Asia, America. 



Subgenus ZONITES (typical). 



Shell depressed orbicular, widely umbilicated, striated above, 

 smooth below, rather solid, whorls numerous (6 or 7), lip sharp, 

 with a slight parietal callus. 



Labial palpi small ; caudal gland reduced to a simple slit. 



Southern Ear ope, Asia Minor. 



The synonyms are JEgopis, Fitzinger, 1833, Tragomma, Held, 

 1837, Helicodes, Dumas, 1847, Verticillus, Moquin-Tandon, 1855, 

 Archseozonites, Sandberger (fossil). 



Subgenus HYALINIA, Ferussac, em. 1819. 



Shell thin, vitreous, fragile, shining, unicolored, corneous; 

 last whorl not descending at the aperture ; peristbme thin, sharp. 



Mucus-pore shallow, hardly distinct, extremity of the tail 

 slightly sinused, skin bluish. 



Northern Hemisphere, species numerous. 



Section YITREA, Fitzinger, 1853. 



Shell small, fragile, shining, hyaline, smooth, convexly de- 

 pressed, perforate or imperforate, aperture lunate. 



Grystallus, Lowe, 1854, is a synonym. 



Section POLITA, Held, 1837. 



Shell depressed or subdiscoidal, umbilicate, smooth, shining, 

 pellucid, corneous, the base more or less milky opaque, aperture 

 obliquely lunate. 



This is the typical group. Its synonyms are Oxychilus, Fitz., 

 1833; Lucilla, Lowe, 1854; Euhyalina, Albers, 1857; Aplostoma, 

 Moq.-Tand., 1855. 



Section ZONITOIDES, Lehmann, 1864. 



The animal differs from the typical Hyalinia in possessing- 

 dart, like the Helicidne ; the shell is a Polita. European. 



