Book Notice. 



359 



rivers. Physa fontinalis, which comes on the outer margin of 

 the Reed-belt, is very abundant, especially in the late winter 

 and early spring. Bithynia tentaculata is perhaps the dominant 

 species following the Physa period, while Limncea pereger and 

 Limncea aiivicularia encroach locally for a short period about 

 May. 



There is an abundant molluscan fauna on the grassy margin 

 of the canal, but there is, of course, little in the way of a true 

 marsh. Siiccinea elegans is typical of this habitat, and very 

 abundant, and there are thriving colonies of Hygromia granulat 

 and H. Jiispida in the patches of Potentilla anserina. 



§ 4. Non-Calcareous Rivers and Streams. 



(All the Rivers, Streams and Becks in the district come 

 under this heading). 



(a) The Smaller Streams (Becks). 



Reed Beit. 



Nil. 



Marsh. 



Pisidiiini piisillitm 



Gmelin. 



Open Water. i 



Ancylus fliiviatilis JMiill. 

 Limncea peveger Miill. 



The above is characteristic of a swiftly-running beck and 

 the full association is dependent on the gradient. In some 

 of the swiftest reaches of the becks Ancylus — the typical 

 mollusc of running water, alone is present, while the Pisidia 

 occupy the more muddy shallows of the lower beck. 



(6) Rivers (Example — R. Lune). 



Open Water. 



Reed Belt. 



Physa fontinalis Drap. 

 Pisidimn amnicum MiiU. 



Marsh. 



Ancylus ftuviatilis Miill. 

 Limncea pereger Miill. 



,, auricularia L. 

 Valvata piscinalis Miill. 

 Neritina fliiviatilis I-. 

 Unio margaritifer I,. 



The species common to both the lower and upper reaches 



are Limncea pereger, Ancylus flnviatilis and Neritina fliiviatilis, 



the latter gradually disappearing towards the source. 



[To be continued). 



The Hull Museum continues tp pour out its penny pamphlets. We 

 have recently received No. 59, A ' List of East Yorkshire Spiders, etc' 

 by T. Stainforth. This includes 177 spiders, 14 phalangidea, and 5 pseudo- 

 scorpions. Nos. 60 and 61 are the usual Quarterly Records, the former 

 containing notes on Hull plans, forgeries, skull of fossil Bison, etc., the 

 other including notes on old Hull ships and shipping, the Brigg pre-historid 

 boat, slavery relics, and media^\-al antiquities. A further (third) edition 

 lias been issued of the Guide to tlie Albion Street Museum, Hull, and con- 

 tains much new matter. 



1909 Oct. I. 



