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, _Helicophanta_, 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 Hæmastoma, H. Contusa, (Streptaxis, 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_, Carocolla, 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 aperture, like the Helicogenæ, but with the whorls increasing very gradually; H. epistylium. _S. gen. 8_, _Cochlostyla_, Bulinus. _S. gen. 9_, _Cochlitoma_, Achatina. _S. gen. 10_, _Cochlicopa_, Polyphemus Glans. _S. gen. 11_, _Cochlicella_, 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 these sub-divisions, for the sake of presenting the reader with the principal variations to which the genus is subject. The established genera will be characterized in their places. Fig. 254 to 281. HELIXARION. Fer. VITRINA, Drap. Differing from Helicolimax in the structure of the animal. Fig. 262. HEMICARDIUM. Cuv. ([Greek: hêmisus], _hemisus_, half, [Greek: Kardia], _cardia_, heart.) CARDIUM Hemicardium, fig. 123**, and several similar species. HEMICYCLA. Sw. A sub-genus of Helix. HEMICYCLONOSTA--see CARDILIA.