HELIX. 313 



back. Right eye retractor passing between primary branches of 

 genitalia. (Frontispiece, fig. 7). 



Jaw well arched, stout, with 3-9 strong ribs denticulating both 

 margins (pi. 67, figs. 1, 4, 7, 8, 9). Radula normal, having the 

 cusps of median and lateral teeth about as long as the squarish 

 basal plates, side cusps small or wanting. Marginals with a long, 

 oblique bifid inner cusp and a small simple or bifid ectocone (pi. 67, 

 figs. 2, 3, 5, 6, 11). 



Genital system characterized by a short penis passing into the epi- 

 phallus, which bears the retractor (distal ly inserted on lung floor) 

 and branches into vas deferens and a flagellum, the latter rarely 

 wanting. One dart sack present and well developed, containing a 

 four-bladed dart, with short neck and crenulated base. Mucus 

 glands two, varying from simple to multifid, but always composed of 

 smooth, tubular coeca ; inserted on each side of vagina immediately 

 above entrance of dart sack; both the dart sack and mucus glands 

 lying free in cavity, not bound together by a stout membrane. Sper- 

 matheca globose, on a long duct, which usually bears ad iverticulum. 

 Ovotestis compact, imbedded in the side of the liver (frontispiece 

 figs. 5, 6, H. pomatia). 



.Distribution, Europe, North Africa, Asia Minor. 



Helix is distinguished from Helicigona mainly by the form of the 

 dart and the free diverticulum ; this being invariably bound to 

 oviduct by a wide membrane in Helicigona. 



The genus Helix contains the most highly organized and complex 

 snails of the family Helicidce. Like the European type of Homo, 

 but unlike most highly specialized forms, their specialization has 

 evidently fitted them for meeting widely diverse conditions of exist- 

 ence. Their powers of reproduction as well as the ease with 

 which they adapt themselves to circumstances of climate and envi- 

 ronment new to them, are remarkable. They love the light, and 

 for the most part are not exterminated by the destruction of their 

 native forests, but accepting kindly the new conditions, live and 

 multiply in vineyards, gardens and around tilled fields. As colo- 

 nists they rank with man, the dog and the horse. Various species 

 live and thrive in the United States, Mexico, Cuba, Argentina, S. 

 Africa, New Caledonia, Australia, etc., etc. None, even of the most 

 widely distributed Helicoids of other genera such as Eulota similaris, 

 iiave so wide a range of climate ; and the species of Helix which 



