MELANIA. 



GENERIC CHARACTER. 



Shell turrited, rather thick, covered by an epidermis ; 

 spire generally elongated ; aperture ovate or oblong, longer 

 than broad, acute above ; labrum simple, acute, prominent 

 near the base and rather abruptly retracted at its junction 

 with the base of the columella, and not united above to 

 the labium ; columella destitute of a fold, arquated to- 

 wards the base ; operculum corneous ; umbilicus none. 



OBSERVATIONS. 



Before Lamarck perceived the necessity of establishing 

 this group, some of the species were variously arranged. 

 Linne, Lister, Schroeter. and others, considered them as 

 belonging to Helix -^ Muller to Nerita and Bummim ; 

 Bruguiere to Bulimiis.and Chemnitz referred one species 

 to Strombm. The genus differs from Helix, Lymneus^ 

 &c., by having an operculum as in Pahidina^ Ampularia^ 

 and Valvata, and from these, ia addition to other differen- 

 tial traits it may be distinguished by the disunion above 

 of the labial. It strongly resembles Mekmopsi.s, Pircna 

 and Potami(h% but these are distinctly and unequivocally 

 emarginated at base. 



The animal respires water : it has a short, conic-cylin- 

 dric, obtuse rostrum ; two acute tentacula having the eyes 

 at their exterior base ; foot short and obtuse. 



PLATE VITI. 



