HELIX. 159 



HELICOPIIANTA. Fer. A sub-genus of Helix, consisting of ear- 

 shaped species with large open apertures. 



HELICOSTYLA. Fer. A sub-genus of Helix, consisting of species 

 with numerous whorls, as H. Epistylium, fig. 281. 



HELISOMA. Sw. A sub-genus of Planorbis. Sw. p. 337. 



HELIX. Auct. Fam. Colimacea, Lam. — Descr. Orbicular, light, 

 generally globular; spire short, last whorl ventricose, aperture 

 oblique, peritreme reflected, interrupted by the most prominent 

 part of the body whorl; columella confluent with the outer lip, 

 and contiguous to the axis of the shell. No operculum ; a thin 

 epidermis. — Obs. The land shells composing this genus are 

 found in all parts of the world; the common snail, H. Aspersa, 

 is well known as a destructive animal in our gardens. The 

 genera Helix, Achatina, Bulinus, Clausilia, Anostoma, &c, have 

 been united under one generic name by De Ferussac, and again 

 divided under the following sub- generic names, each of which we 

 shall illustrate by a figure. Genus Helix : Sub-genus 1 , Helico- 

 phanta, consisting of species with large apertures, like Vitrina ; 

 Helix brevipes. S. gen 2, Cochlohydra, Succinea Amphibia, 

 Drap. S. gen. 3, Helicogena, consisting of the common species 

 with the last whorl large; Helix Hsemastoma, II. Contusa, (Strep- 

 taxis, Gray,) H. Aspersa. S. gen. 4, Helicodonta, consisting of 

 species with teeth or folds on the columella; Polydonta, Montf. 

 Anostoma, Helix Nux-denticulata. S. gen. 5, Helicigona, Caro- 

 colla, Geotrochus. S. gen. 6, Helicella, consisting of depressed 

 species with a large umbilicus ; H. Citrina (Naninia, Gray.) 

 S. gen. 7, Helicostyla, consisting of species with a simple aper- 

 ture, like the Helicogense, but with the whorls increasing very 

 gradually; H. epistylium. S. gen. 8, Cochlostyla, Bulinus. S. 

 gen. 9, Cochlitoma, Achatina. S. gen. 10, Cochlicopa, Poly- 

 phemus Glans. S. gen. 11, CocJilicella, Bulinus decollatus. »S. 

 gen. 12, Cochlogena, Azeca tridens. S. gen. 13, Cochlodonta, 

 Pupa Uva. S. gen. 14, Cochlodina, Clausilia macascarensis, 

 Balea fragilis. The last three sub-genera are included in the 

 genus Odostomia of Fleming. We give an example of each of 



