166 HELIX. 



slight callosity.— 05«. This genus of land shells, distinguished 

 from the genus Helix, by having an operculum and a thickened 

 columellar lip, differs also from Cyclostoma in having the 

 aperture semicircular or angulur, the peritreme discontinuous 

 and the operculum concentric. These shells are generally small 

 in size, and simple in form. Lamarck describes only three or 

 four species. Mr. Gray described some others in the Zoological 

 Journal, 73 species are given in the Monograph, No, 1, Sow- 

 erby's Thesaurus. " Oligyra" of Say is given to this genus in 

 Grray's Synopsis, because Lamarck applied " Helicina" first to 

 Eotella,. Helicina Major and similar species having a notch in 

 the peritreme, have been separated under the name Alcadia 

 (our figs. 306, 307.) H. Aureola, Thesaurus Conchyliorum, 

 PI. i. fig. 43, 4, 5, having a peculiar contraction near the outer 

 lip, is named genus " Luoidella," and the sharp-keeled, Caro- 

 colla-formed species (our figs. 532, 533), has been named genus 

 " Teochatella." The passage by intermediate species is, 

 however, so gradual, that these generic distinctions can hardly 

 be maintained. 



HELICITES. B1. Part of the genus Nummulites, Lam. Eo- 

 TALiTES and Egeon, Montf. 



HELICOGENA. Eer. A sub-genus of Helix, consisting of 

 species, which, like the common garden snail, fig. 268, are glo- 

 bose and simple in form. 



HELIOCOLIMAX. Eer. Viteina, Drap. H. Pellucida, 

 PL siii. fig. 263. 



HELICOPHANTA. Eer. A sub-genus of Helix, consisting of 

 ear-shaped species with large open apertures. 



HELICOSTYLA. Eer. A sub-genus of Helix, consisting of 

 species with numerous whorls, as H. Epistylium, PI. xiv. fig. 281. 



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



HELIX. Linnaeus. Fam. Colimacea, Lam. — Descr. Orbicular, 

 light, generally globular ; spire short, last whorl ventricose, 

 aperture oblique, peritreme reflected, interrupted by the most 

 prominent pai't of the body whorl ; columella confluent with the 

 outer lip, and contiguous to tlie axis of the shell. No oper- 



