3i6 



Geographical Distribution of MoUusca, 



are extensive deposits of e^^tuarine and maritime silts, and 

 within land is an almost universal mantling of glacial drift. 

 In low valley bottoms, remnants of peat moors still continue 

 as relics of the ancient landscape of Lonsdale. Rivers, ditches, 

 pools and the like afford variety of open water, between the 

 soft peat}^ floods of the mountain becks and the hard clear 

 issues of limestone springs. 



Few districts shew a greater variety of vegetation. Of the 

 lull series of British marshlands and moorlands few formations 

 are unrepresented. Dry grasslands show all possible variety 

 between the natural pasture of the calcareous rocks and the 

 Calluna heath and moor of the grit and shale fells. In the 

 old times the forests of Ouernmore and Lonsdale were doubtless 

 wider spread with woodland, though to-day there is an abun- 

 dance of naturally occurring woodland of Ash and Oak to which 

 recent forestry has added woods of Beech and Pine. 



The classification of the formations or groups of associations 

 into which the district may be divided for purposes of biological 

 research, here made applicable to land and freshwater mollusca, 

 is that derived from a consideration of the vegetation not only 

 of the present district, but of many other parts of Britain. 

 Within the limits of the present paper the responsibility for 

 its employment rests upon Mr. Rankin, while the grouping of 

 the mollusca into associations is that of Messrs. Kendall and 

 Dean. 



THE BIOLOGICAL FORMATIONS OF SOUTH LONSDALE. 

 Type of Coastlands. 



1. Salt Marshlands. 



Transition to Freshwater Marshlands. 



2. Sand-dunes. 



(Not typically developed). 

 Type of Dry Grasslands. 



Calcareous Pastures. 



Non-calcareous Pastures and Heaths. 

 Type of Wet Grasslands. 



1. Formations of Hard-water Lakes and Ponds. 



2. Hard-water Rivers and Streams. 



3. Soft-water Lakes and Ponds. 

 3(2 ,, Canals. 



4. Soft-water Rivers and Streams, 



5. Heath Moors. 



Naturalist, 



