NELSON : ON THE LIMN^EID^. 263 



our visit, between the bank and the water was a wide expanse 

 of soft mud, on which we could not find a single track left by a 

 crawling mollusk, and not being provided with strong nets with 

 which to search for the Unionidae we lost no time in vain 

 regrets, but resolved to try and retrieve the day in some other 

 direction. 



Leaving the canal at the first road to the left, we soon 

 came to a ditch where we obtained specimens of LinmcBa 

 peregra and LimncRa trtincatula. Here I observed a very un- 

 usual sight, namely Limnaa trimcatula in the act of floating. 

 The LimncBtdce as a Family seem to be very fond of floating on 

 the surface of the water with their shells downwards, more 

 especially Limncsa peregra, L. stagnalis, L. glabra and Physa 

 hypnorum, whilst Limncea auricidaria I have never yet seen 

 floating, and before to-day I had not seen Limncea truncatula 

 performing this action. 



Leaving this ditch we passed some distance alongside a 

 hedge bank and saw specimens of Helix nemoralis and Helix 

 ca/itiafia, and resting on a blade of grass a beautiful small 

 butterfly which I found was the Small Copper. 



A little further on this lane we came to a place called Cow- 

 bridge. Here is a rather broad drain which seems to have been 

 somewhat recently cleaned out. There were no weeds growing 

 in it, but here and there very sparsely distributed were small 

 straggling tufts of grass-like plants with one or two small loose 

 patches of Callitriche. There after considerable searching we 

 obtained examples of LimncEa peregra, L. palustris, Physa 

 hypnorufti, Flanorbis spirorbis and PI. marginatus, and my com- 

 panion obtained a single specimen of Liinncza glabra this — 

 combined with the Physa hynomm — proving that they had 

 been washed down the slowly flowing drain from no doubt some 

 smaller and more luxuriantly weed-grown ditch. A word or 

 two here respecting the association of Limncea glabra with 

 Physa hypnorum and Planorbis spirorbis ; though not invariably 

 found together, as a rule they are generally found in the same 



