1817.] GENUS PALUDINA. 125 



SPECIES. 



A. rivularis* ' iSAe// corneous, opake, conic -depressed, 

 apex obtuse, nearer to, and leaning towards, one side and 

 one end; aperture oval, rather narrower at one end, entire; 

 within milk-white. 



Lengdi one fourth of an inch. 



Cabinet of the Academy. 



Common, adhering to stones in rivulets: the animal 

 resembles the inhabitant of shells of tlie genus Lymnsea, 

 the tail is very obtuse rounded. 



Genus PALUDINA. Lam. Latr. 



Shell subovate, operculated; aperture entire, longitudi- 

 nally ovate, narrowed above; lip simple, not dilated or re- 

 flected. 



Ohs. This genus has been very lately separated by 

 Mr. Lamarck from the Cyclostoma^ with which it cor- 

 responds, except in having no dilated lip, and the aperture 

 is angulated above. The animal has a short rostruhi, two 

 acute tentacuia with eyes at thtir external base, a small 

 membranaceous wing each side of the body before, foot 

 double before, the wing of the right side is folded into a 

 small canal, by which the water is introduced into the 

 respiratory canal. Latr. To this genus will be referred 

 several' of the Lymnaea of the American Edition of Nich- 

 olson's Encyclopaedia as L. decisa, vivipara and suhca- 

 rinata. 



SPECIES. 



P. limosa* Shell conic, subumbilicate, dark horn 

 coloured, generally incrusted wuh a blackish irregular 



