102 INOPERCULATA. 



form, as in the lower or less developed members of a group : 

 thus in B n limns it is many-whorled, in Omalonyx rudimen- 

 tary; in Vitrina spiral, while in Parmacella it is shield- 

 like; in Oleacina produced, but in Testacella ear-shaped- 

 in Nanina helicoid, while in Avion it is granular ; in Helix 

 spiral, but in Limax simple and flattened; in Auricula 

 well-developed, but in Otina rudimentary; in Limneus 

 elevated, but in Ancylus patelliform ; in Amphibola tur- 

 binate, in Sijphonaria conical and limpet-like. 



Order INOPERCULATA. 



Teeth nearly similar, very numerous, placed in many cross 

 liues on a more or less elongated lingual band; mouth 

 usually with transverse jaws. Respiratory organ in the form 

 of an air-sac, or dorsal cavity lined by a vascular network ; 

 edge of mantle covering the pulmonary cavity, except at a 

 lateral aperture. Animal hermaphrodite, with reciprocal 

 impregnation. 



Usually phytophagous, and respiring free air. 



The Inoperculate Pulmonifers are usually active and well- 

 organized Gasteropods, with distinct heads furnished with 

 teeth, jaws, well- developed eyes and tentacles, and they crawl 

 on an extended locomotive disk, or foot. The free air they 

 breathe is passed over a network of vessels for the purpose 

 of aerating the blood; and, in the majority of instances, they 

 are protected by well-developed spiral shells. Chiefly her- 

 bivorous, they feed upon the vegetation of the earth. They 

 either live upon the land (Geop/tila) ; or are inhabitants of 

 fresh-water, coming to the surface, however, to breathe (Li/u- 

 nophila) ; or they are denizens of salt-marshes and places 

 near the sea (Thalassophila). 



