32 2 MILNE AND OLDHAM : MOLLUSCA OF BOWDON DISTRICT. 



Physa fontinalis. "In the ponds on Baguley Moor" (Dyson). 

 Also at Ashley Mill, Agden, Warburton, Sale Meadows, 

 and Mere. 



Limnaea peregra. Universally distributed and very variable. 

 Is one of the causes of variation in size of this species to be 

 found in the plants among which it lives ? In ponds, 

 especially, where there are large leaved plants, as — Nym- 

 phcea — the shells are usually large, and frequently covered 

 with green slime, matching the leaves. Among Potamoge- 

 ioji, the specimens are smaller ; while in ponds where only 

 Lemna grows the Limncece are generally slight, and with 

 transparent shells, showing the markings of the mantle. 

 The smallest are found in pools, where there is only 

 confer void growth on stones, and here they appear uni- 

 colourous. (This rule, however, is not universally applic- 

 able ; in some cases other means of self-preservation seem 

 to have been more efficacious than assimilation to surround- 

 ings). The same principle may be applied to the other 

 LimncEce. 



L. peregra var. ovata. Found almost as commonly as the 

 type. 



L. peregra var. labiosa. A very labiate form occurs at 

 Ringway, which may deserve separate mention. 



L. auricularia. A few specimens have been taken in Hamp- 

 son's Pit. 



L. stagnalis. Sparingly distributed. At Dunham Wood- 

 houses, Agden, Mobberley Mill (now drained), Heyhead, 

 Northen Etchells, Brooklands, and Hampson's Pit. The 

 species was introduced to the last locality from Northen 

 Etchells in 1884, the average length of the specimens at this 

 place being 37 mm. By 1S90 they had attained an average 

 of 47 mm. in their new abode. 



L. palustris. Plentiful and widely distributed. 



J.C., vii., Jan. 1894. 



