LIMN.EA. 



253 



They roay frequently be observed floating on the surface 

 of the water with their shells downwards, and progressing 

 by an undulating motion of the foot; when the ponds 

 are dried up in seasons of drought, the animals bury 

 themselves in the mud, strengthen the outer lip of their 

 shells by an internal rib, and close the aperture by means 

 of an epiphragma, like the Helicida during the period 

 of hybernation. 



Species of Limnaa. 



acuminata, Lam. 

 acutalis, Morel. 

 aftinis, Beck. 

 ampla, Migh. 

 amygdalus, Trosch. 

 appressa, Jay. 

 cblamys, Bens. 

 columella, Say. 

 conoidea, Say. 

 jugularis, Say. 

 Karpinskii, Siemasch. 

 lepida, Gould. 

 lineata, Say. 

 longula, Mouss. 

 luteola, Lam. 

 Moreletiana, Gassies. 

 Natalensis, Krauss. 

 Ouhonensis, Eyd. 



oval is, Guv. 

 pallida, Guer. 

 papyracea, Spits. 

 pa tula, Trosch. 

 perlrevis, Conr. 

 Petitii, Beck. 

 pulchella, Beck. 

 pumila, Kryu. 

 rufescens, Gray. 

 rustica, Andrz. 

 stagnalis, Linn. 

 succiniformis, Shuttl. 

 Timorensis, Sow. 

 ventricosa, Siemasch. 

 Virginiana, Lam. 

 viridis, Quoy. 

 volutata, Gould. 



Sub-gen. neritostoma, Klein (Radix, Montf. Gulnaria, Leach). 



Shell sub-ovate, last whorl ventricose ; aperture more than 

 half the length of the shell, greatly expanded. 



auricularia, Linn. 

 Balthica, Nilss. 



Burnettii, Alder. 

 crystallina, Ziegl. 



VOL. II. 



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