22 ZONITID^. 



Helicarion, Fer., 1821. 



Syn. — Anstenia, Nevill. ?Hoplites, Theobald, 1864. 



Distr. — 95 sp. India, East Indies, Philippines, Australia, 

 Abyssinia. H.Jiammulata, Quoj^ (xcii, 77). Celebes. 



Shell heliciform, rounded-oval, thin, fragile, covered with a 

 verj^ light epidermis ; spire short, whorls few, the last much 

 swollen; aperture large, oblong-triangular; peristome simple, 

 sharp. 



Animal not entirely retractible within the shell ; mantle pro- 

 duced in front into two lobes upon the neck, and posteriorly, on 

 the right side into a lobe partly covering the shell ; foot truncated 

 behind, the sole divided longitudinall}^ into three parts. 



zoNiTARiON, Pfeffer, 1883. Jaw without middle tooth. H. 

 semimembranaceus, von Martens. 



OTESiA, H. and A. Adams. (Vitrinella, Gray.) Mantle-lobe 

 covering the greater part of the shell. Shell imperforate, very 

 thin, spire conic. 



Family ZONITID.E. 



Animal able to withdraw completely within its shell ; provided 

 with a caudal mucous pore. Jaw produced in the middle. 

 Lateral teeth bicuspid, marginals acuminate, unicuspidate or 

 bicuspidate. 



Shell usually depressed heliciform, umbilicated, thin, more or 

 less transparent, with simple, sharp peristome. 



The hyaline structure of the shell and the acute margin of the 

 aperture most readily distinguish these shells from the Helicidse, 

 with which they are usually confounded. 



ZoNiTES, Montfort, 1810. 



Syn. — Archasozonites, Sandb. 



Distr. — Europe and America. Fossil. Tertiary. 



Shell subdepressed, umbilicated, very thin, more or less trans- 

 parent; aperture semilunar, usually without teeth; lip thin, 

 sharp. 



Animal elongated, completely retractile within the shell ; jaw 

 with a well-marked middle rostrum, lateral teeth bicuspid, mar- 

 ginals unicuspid, sharp ; foot with caudal mucous pore or slit. 

 The Asiatic group Ariophanta has a similar shell,-but the mantle- 

 lobes are reflected upon it. 



ZONITES (restricted), (^gopis, Fitzinger, 1833. Tragomma, 

 Held, 1837. Helicodes, Dumas, 1847. Yerticillus, Moquin- 

 Tandon, 1855.) Labial palpi small ; caudal gland reduced to a 

 simple gioove, shell depi'essed orbicular, widely umbilicated ; 

 striated above, smooth below ; lip sharp, with a slight callus on 

 the parietal wall. Southern Europe, Asia Minor. 12 sp. Z. 

 Algirus, Linn, (xciii, 92J). 



