LIMNvEUS. 65 



flat, with a very small deep umbilicus. Body whoii 

 extremely large filling nearly the whole surface, the 

 circumference of which slopes gradually and rather 

 convexly to an angulated edge, which is below the 

 centre of the shell. 



Hah. Somewhat common in the south of Ensfland, 

 but becomes more rare towards the north. Its north- 

 ernmost English locality is near York. It is recorded 

 as occurring in the south of Scotland. Ditches and 

 ponds of stagnant water, containing aquatic plants, 

 are its favourite resorts. 



LiMN-ffiius. Draparnaud. 



Shell — Ovate, dextral, diaphanous; aperture ovate, hounded 

 hy an entire margin, without operculum. 



Animal — With a hroad head and compressed tentacles, with 

 eyes at their inner hases ; mantle simple. 



L. PEREGER. Muller. PI. VII, fig. 41. 



Shell striolate, more or less ventricose ; spire short, rather acute ; 

 wkorls convex. 



Helix putris, Penn. Limnseus ovatus, Drap. Lim- 

 neeus vulgaris, Pfeif., 8^c. 



This commonest of our fluviatile moUusks, is of an 

 infinite variety of forms and shapes ; two or three of 

 the principal of which we will endeavour to describe. 

 The shell of the normal form is of a greyish or yellowish 

 colour, thin, not fragile, glossy, concentrically striated ; 

 slightly wrinkled longitudinally ; spire more or less 

 depressed, consisting of four whorls. Mouth large, 

 oval, oblong, but peaked above ; umbilicus small, 

 sometimes nearly obsolete. 



var. OVATA. Ventricose, with an acute but ex- 

 ceedingly short spire. Body whorl much expanded, 

 forming a capacious mouth. 



var. LiNEATA, body large, spire not long, with the 

 apex often corroded ; generally of an olivaceous ferru- 

 ginous colour, the outer whorl lineated. 



var. MARGIN ATA, Micliaud, has the internal lip of 

 the outer rim thickened. 



r 



