Geographical Disfn'bii/ion of Molliisca. 



3. Large Lakes. 



Open Water. 



Limncea pereger MiUl. 

 Planorbis albus L. 

 Ancyliis fliiviatilis Miill. 



Example — Lake Windermere. 



Reed Belt. 

 Physa fontinalis L. 



Marsh. 



j Succinen elegaiis Kisso 



Avion snbfuscus Drap. 

 Agriolimax l(Bvis Miill. 

 \ ZtDiitoidcs iiilidiis Miill. 

 J:iu oiiiil us fii/'i'iis iNIi'il!. 



Alley! US fiuviatilis occm"S principally near the outflow, that 

 is in practicalh^ fluviatile waters. Arion siihfiiscus is the domi- 

 nant species on the lake margin. Z. nitidus is typically a 

 non-calcareous marsh species, corresponding to the allied 

 species Z. excavatus on drier ground. 



In this section also comes : — 



Anode nta cygnea L., which is characteristic of a non-cal- 

 careous lake or pond with a muddy bottom. It is abundant 

 where it does occur, just as in the canal it takes entire possession 

 of the deeper water. No definite association of the habitat 

 can be given ; probably it is solitary. It is worthy of note that 

 the largest known specimens (measuring nine inches in length) 

 have been taken from a pond near Garstang. 



Sub-section 3a. — Soft Water Canals. (Example — Preston 

 and Kendal Canal). 



Open Water. 



Limncsa pereger Miill. 



aiiricularia L. 

 Planorbis albus L. 

 Valvata piscinnlis ^Nliill. 

 Anodonta cygnea L. 

 Pisidiiini amnictan Miill. 

 Sphcsriiiin laciistre iNIiill. 



Marsh. 



L. truncatula Mull. 

 Pis. pusillum Gmelin. 

 Succinea putris L. 



„ elegans Risso 

 Agriolimax agrestis L. 



Icsvis Miill. 

 Arion aier L. 



,, hovtensis Fer. 

 Vitrea crystallina Miill. 



radiatula Alder. 

 Z. nitidus Miill. 

 Eiic. fulvus Miill. 

 Hygromia granulata Aid. 



hispid a L. 

 Cochlicopa lubrica Miill. 



As will be seen and as might be expected, the molluscan 

 fauna places the canal intermediate between non-calcareous 

 lakes and non-calcareous rivers. In the open water section 

 there is a striking abundance of hoth. Anodonta cygnea and 

 Neritina fiuviatilis, the former a species prevailing in the deeper 

 non-calcareous ponds, and the latter typical of slow-flowing 



On Rocks 

 Neritina fliiviatilis L. 

 {Dreissensia polymorpha 

 Pallas).* 



Reed Belt. 



Acroloxus lacustris I>. 

 Limncsa palustris Miill. 

 Planorbis umbilicatus 



Miill. 

 vortex L. 

 fontaniis 



Lightfoot. 

 Physa foiitinalis Drap. 

 Bithynia tentaculata L. 

 V alvata cristata Miill. 

 Sphcerium corneum L. 

 Pisidium fontinale Drap. 



milium Held. 



* An introduced alien. 



Naturalist 



