298 HELICIGONA. 



b. Acutely keeled ; lip continuous across parietal wall. 



HELICIGONA. 

 bb. Depressed, not keeled ; or if keeled the lip-ends remote, 



Chilostoma, Fridicocampylcea. 

 bbb. Subglobose, with narrow or closed umbilicus. 



c. Baso-columellar lip broadly reflexed, Tacheocampylcea. 



cc. Lip narrow, dilated only at insertion, Arianta. 



aa. Spire flat, sunken in middle ; mucus glands short, triangular, 



ELONA. 

 2. Aperture ear-shaped, 3-toothed, ISOGNOMOSTOMA. 



TERTIARY GROUPS. 



1. Shell with'pappillre arranged in oblique series as in H. setosa, 



a. An obtuse angle around umbilicus; periphery rounded, 



TROPIDOMPHALUS. 

 aa. Umbilicus narrow or closed ; periphery acutely keeled, 



Metacampylcea. 



2. Shell without regularly placed pappillse. 



a. Large, depressed, with broad peristome, MESODONTOPSIS. 

 aa. Subglobose, spire conoidal, peristome narrow, 



GALACTOCHILUS. 



Section Helicigona (Fer.) Risso. 



Helicigona FER. 1. c. (in part). Risso, Hist. Nat. Eur. Me"rid. iv, 

 p. 66, first species H. lapicida. Caracolla TURTON, Man. L. and 

 Fr.-W. Sh. Brit. Is., 1831, p. 66, and of some other authors. Chilo- 

 trema LEACH in Turton, 1. c., p. 66, and of Beck, et al. Latomus 

 FIT/., Syst, Verz., 1833, p. 97. Lenticula HELD, Isis, 1837, p. 913. 



Shell urabilicate, depressed, lens-shaped and acutely keeled ; surface 

 minutely granulous, horn-colored or dusky, obliquely streaked with 

 brown ; last whorl deeply deflexed below the keel ; aperture very 

 oblique, oval, angled at keel, the peristome reflexed below, thick- 

 ened within, continuous and raised across the parietal wall, toothless. 

 Type H. lapicida, pi. 43, figs. 22, 23. 



Jaw with four strong ribs ; radula having no side cusps on middle 

 and lateral teeth ; marginals developing an ectocone, and the large 

 cusp become bifid. Geuitalia (pi. 62, figs. 20, 21, H. lapicida) with 

 penis, epiphallus and flagellum as usual. Two long mucus glands; 

 dart-sack containing a curved dart with cylindrical shaft and short, 



