PALUDINA. 17 



About three-eighths of an inch long, and a quarter 

 of an inch broad. Convex or flat above, and slightly 

 incurved underneath. 



Hah. Rivers, especially the larger ones, as the 

 Thames, Trent, Ouse (near York), Humber, Severn, 

 and Avon. We have frequently obtained dead speci- 

 mens from the ballast hills near Middlesbro', which 

 have been brought from the mouths of other rivers. 



PALUDINIDiE. 



Paludina. Lamarh. 



Shell — Spiral, convex ; mouth nearly round, operculum long, 

 consisting of concentric rings, terminating in a small 

 nucleus on the inner side ; epidermis coloured. 



Animal — With a lengthened muzzle ; foot large ; tentaculce 

 two, those of the male unequal. Female ovo-viviparous . 



P. LiSTEHi. Forbes and Hanley. PI. IV, fig. 5, 

 and PI. YIII, fig. 3. 



Shell thin, spii'al ; five volutions very distinctly marked ; mouth 

 large and open. 



Paludina vivipara. Gray. 



This shell is chiefly found in the midland and south- 

 ern counties. It may be distinguished from P. vivipara 

 by the volutions being more inflated, the shell thinner, 

 the last whorl larger and more open, and the whorls at 

 the apex very distinct, and terminating in a sharp point. 



Full grown individuals measure about an inch in 

 length, by three fourths of an inch in breadth. 



Hah. Slowly-running rivers and canals. The re- 

 corded localities are the rivers Ex, Taw, Lea, Isis (at 

 Blenheim), and a stream near York, &c. 



P. VIVIPARA. Linnceus. PI. IV, fig. 6. 



Sharper, and more produced than the last. Shell rather thicker and 

 not so translucid; volutions six in number, with brown bands running 

 parallel with the sutures. The colouring paler, the whorls less 

 prominent, and consequently the sutures not so deep ; mouth more 

 contracted ; apex blunt. 



Paludina achatina. Gray, Lam, 8fc. 



Length the same as P. Listeri, but not quite so broad. 

 Hah. Abundant in the Cherwell, Oxfordshire, &c. 



