IIO OLDHAM I LAND AND FRESHWATER MOLLUSCA OF CHESHIRE. 



country are too swift to suit the habits of any species but Ancylus 

 Jluviatilis and the ubiquitous Limncza peregra, and that after 

 reaching the plain, apart from their frequently polluted condition, 

 they flow over stony beds and lack the aquatic vegetation which 

 characterises more sluggish streams. Those canals, however, which 

 are still unpolluted, contain several interesting species ; and the 

 many meres, which are such a pleasing feature in the Cheshire 

 landscape, afford a home for others. In addition to the meres and 

 larger pools, the whole plain is studded with small ponds, or 'pits' 

 as they are called locally, whence in former days the farmers 

 obtained marl for manuring their fields. Many of these pits are 

 now choked with vegetation and are well stocked with Umnma 

 and Planorbis, whilst in their muddy bottoms various species of 

 Anodonta, Spharium and Pisidium flourish and abound. There are 

 none of these marl-pits in the hill country, where freshwater shells 

 are as scarce as those inhabiting the land. 



Unio margaritijer is found in the upper reaches of the Dee, 

 beyond the county border, but, so far as I know, it has never been 

 taken in Cheshire waters. U. pictorum and U. turn id us are very local, 

 and are absent from many of the meres and larger pools, where one 

 would expect to find them associated with the two species of 

 Anodonta which abound in such habitats. 



The freshwater Gastropods are well represented ; Amphipeplea 

 glutinosa and Neritina jluviatilis being the only noteworthy absentees. 

 Several of the canals and streams are apparently well suited for the 

 requirements of the latter species, and its absence is curious. 

 Lnnncea involuta, a doubtful species, which is confined to one Irish 

 station, together with Planorbis dilatatits and Paludestrina jenkinsi 

 are the only other members of the class which do not occur; and it 

 is not improbable that the two last will before long find their way 

 into some of the Cheshire canals. 



Our subject can already boast of a considerable literature, which 

 consists mainly of lists of species which have been taken in various 

 restricted localities. I believe, however, that no attempt has 

 hitherto been made to focus this knowledge into an account of 

 the fauna of the county as a whole. 



L 



The following are the principal lists which have come under my 



notice : 



David Dyson. — 4 Land and Freshwater Shells of the District 

 around Manchester.' 1850. 



Isaac Bverlev. — Fauna of Liverpool [Proc. Liverpool Lit 



and Phil. Soc, 1853-1S54, Appendix". 



Naturalist, 



