126 HELICIDiE. 



species are figured by Ferussac in his great work, each with 

 a caudal shell, but more information is required concerning 

 them. 



Species of Plectrophorus. 



corninus, Base. Orbignyi, Ferns. 



costatus, Bose. 



Fam. HELICID^E. 



Body spiral, distinct from the foot. Teeth on lingual 

 membrane in numerous, straight, transverse lines, equal, 

 uniform, and with the edge-teeth serrated or dentate. Head 

 well-developed ; mouth with a dentate upper jaw or man- 

 dible ; eye-peduncles and tentacles retractile under the skin. 

 Mantle-margin not extended, or produced into lobes ; respi- 

 ratory orifice on the right side, under the edge of the shell. 

 Foot elongated, with the hind part simple and pointed 

 behind, not glanduliferous. Orifice of reproductive organs 

 at the base of the right eye-peduncle. 

 Shell external, well developed, spiral. 

 Animal entirely retractile within the shell. Herbivorous. 

 The animals of this family, comprising the " True Snails," 

 are strictly phytophagous, subsisting chiefly on the foliage 

 of trees and plants. Their lingual teeth, very numerous 

 and nearly similar, are placed in many cross lines on the 

 more or less elongated lingual band ; the transverse lines are 

 usually straight, and the form of the teeth varies according 

 to the genus ; in general, the teeth have a broad, expanded, 

 more or less four-sided, oblong base, with a reflexed tip, 

 the bases of the teeth in the same series being close to- 

 gether on the lingual band so as to form a close-set rasp. 

 The animals are entirely retractile within the shell, the 



