ro LIMNjEIDJE. 



ochreous-brown, slightly striate in the line of growth, and in- 

 distinctly so, spirally ; epidermis extremely thin ; whorls 5-7, 

 rounded, and somewhat compressed laterally, body whorl 

 larger than the rest of the shell ; spire produced, obtuse at the 

 tip ; suture rather shallow ; vioiith narrowish oval, acutely 

 angular above, rounded beneath ; outer lip thin ; inner lip 

 spread on the base of the penultimate whorl; pillar with a 

 broad fold. 



Inhabits sluggish streams, ponds, and ditches, on 

 aquatic plants, in most parts of the British Isles, but 

 it is local. It is rather an active mollusc, often leaving 

 its native element to crawl upon those leaves and 

 stems of surrounding plants which are not sub- 

 merged ; at other times it floats in an inverted 

 position on the under surface of the water. The 

 eggs, which are oval, are deposited in gelatinous 

 masses, each of which contains from eight to twenty. 

 The young are hatched in about fifteen or sixteen 

 days, and have a small obtuse shell ; they arrive at 

 maturity in two years. 



B. Mantle lobed ; shell not covered with an 

 epidermis ; spire short. 



2. P. fontina'lis,* Linn:^.. Pl. IV. 



Body rather transparent, greyish or slaty-grey, sometimes 

 shghtly tinged with either a violet or faintly greenish hue ; 

 maritle with two lobes, one of which is split into six and the 

 other into nine finger-like lobes, or divisions, which, when 

 expanded, lap over the shell ; tentacles rather slender, slightly 

 transparent, ash-colour ; eyes moderately large, black ; foot pale 

 grey, rounded in front, ending in a narrow tail. 



Shell ovate, very thin, fragile, glossy, transparent, pale greyish 



* Inhabitini? fountains. 



