298 MOLLUSCA. 



found together, and they are most prolific. One may find 

 them at all times of the year. The shells are elongated and 

 conically oval, the spire being produced, while the snail's 

 body is twisted up in the spire of the shell. They have a 

 prominent head and an oblong foot, notched in front and 

 rounded behind. The shells are extremely variable, one 

 species {Limiwus peretjer) having at least fourteen varieties. 

 In this country the two species important to us are L. trun- 

 i-alulua and L. pereger. Both are hosts of the all-important 

 liver-fluke {Disiotnum hepaticwn) which causes the "liver-rot" 

 in sheep. 



L. truncatidus (fig. 173, a) is a pale ashy-grey turreted shell 

 with five or six whorls, the last whorl being large and expanded, 

 and occupying about three-fifths of the 

 shell ; the spire tapers to a very fine 

 point. It is found nearly all over 

 Britain and Europe, Afghanistan, ilo- 

 rocco, Algeria, the Canary Islands, &c. 

 This snaU lays its ova or spawn upon 

 Fig. 173.^Wati:e.-bnails ^^d around ixinds, ditches, and 

 (Limm.ida). streams. Each snail lays about 1500 



L.pmger. Twice iiat. size! o^ a, m batches of 30 to 100. ihey 

 are deposited in strips of some gelatin- 

 ous substance. Incubation takes place in about two weeks. 

 This is the chief host of the li^'er-fluke. 



L. ppi-eijer (fig. 173, b), the other fresh-water snail, is almost 

 transparent yellowish - brown, and spirally striate, with five 

 whorls. This species often wanders far from water, and may be 

 found crawling up wiUow-trees and in damp meadows. They 

 are carnivorous in habits. Although the embryos of the liver- 

 fluke are found in this species, it seems it cannot complete its 

 changes in it. Were there no Limnwidee there would be no 

 liver-rot in our flocks ; but it is extremely diflicult to destroy 

 these molluscs. There is no doubt that the suggestion made by 

 Miss Ormerod of clearing out shallow pools of weeds, and re- 



