34 MOLLUSCA, 



Some of these have ribs projecting internally*, and there are 

 others in which the last whorl is suddenly recurved, (in the adult,) 

 assuming an irregular and plaited formf . 



ViTRiNA, Drap. — Helico-Limax, Feruss. 



The Vitrinse are Helices with a very thin flattened shell, without 

 an umbilicus ; the aperture large, but its margin not tumid ; the 

 body too large to be completely drawn into the shell ; the mantle has 

 a double border;]:, the upper one, which is divided into several lobes, 

 extends considerably beyond the shell, and being reflected over it, 

 polishes it by friction. 



The known Eiu-opean species inhabit wet places, and are very 

 small§. Hot climates produce larger ones/ 



There are some species of Helix, in which the body can hardly 

 enter the shell, although not furnished with this double border, which 

 should be approximated to them ||. 



When the crescent of the aperture is higher than it is wide, a 

 disposition which always obtains when the spire is oblong or elon- 

 gated, it constitutes the 



BuLiMUs Terrestris, Brug. 

 Which requires a still further subdivision : 



BuLiMus, La7n. 



Margin of the aperture tumid in the adult, but without denta 

 tions. 



Hot climates produce large and beautiful species, some of which 

 are remarkable for the volume of their ova, the shell of which is of a 

 stony hardness ; and others for their left shell. 



Several moderate-sized or small species are found in France, 

 one of which, the Helix decollata, Gm.; Chemn., cxxvi, 1254, 

 1257, has the singular habit of successively fracturing the whorls 

 of the summit of the spire. This is the example referred to, as 

 a proof that the muscles of the animal can be detached from 



* Hcl. sinuafa ; — //. lucenia; — H. lychnuchus ; — H. cepa; — H. isognomostoma ; — 

 H. sinuosa ,- — H. punctata, &c. 



f Ilfl. ringens, Chemn., IX, cix, 919, 920, the Axostoma of Lam., or Tomo- 

 GERES, Montf. ; an analogous fossil shell is the Strophostoma, Deshayes. See, 

 also, pi. V, vi, vii, \'iii, of Draparn., with the accompanjnng descriptions ; the works 

 of Sturm and Pfeiffer on the German species, but particularly see the splendid folio 

 of M. de F^russac on the " Mollusques terrestres et fluviatiles." 



+ Termed by M. de Ferussac " une curiasse et tin coUrlier." 



§ Hel. pellucida, Mull, and Geoff. ; Vifrina peUucidu, Drap., VIIT, 34 — 37": — 

 the He/iconon, Quoy and Gaym., Zool. de Freycin., pi. Ixvii, 1; F<^russ., pi. ix, 

 f. 1—4. 



II lie], nt/a und brevipcs, Feruss., Drap., VIII, 26 — 33. 



