34 



THE LAND AND FRESHWATER SHELLS OF MORECAMBE, 

 LANCASTER, AND DISTRICT. 



By J. DAW DEAN. 



(Read before the Society, November 14, 1906). 



Although much has been written from time to time in the pages of 

 the Journal concerning many of the species of moUusca to be found 

 in the district, I venture to hope that the following notes and list will 

 be of interest to collectors. 



The distribution of the land shells is largely affected by the nature 

 of the rock formation. Morecambe is built, partly on the alluvial 

 deposits, and partly on the sandstones that appear at several points 

 along the coast. Lancaster, the fertile districts to the south, and the 

 villages mentioned in the Lune valley, largely owe the wealth of their 

 agricultural products to the presence of a rich subsoil overlying the 

 millstone grits and shales. " Lancaster stone " has been used almost 

 exclusively on the buildings of the old town and neighbourhood. 



The carboniferous limestone lies to the north, about six miles away, 

 and the county boundary of Lancashire and Westmorland follows a 

 line cutting through the richest part of the limestone district. K small 

 triangular portion is in Lancashire West (v.c. 60), another portion is 

 in Lancashire Furness, and a third and larger portion in Westmorland. 

 The Furness section, having been assigned by the authorities to West- 

 morland, it will be seen at once where many of the rarer species, given 

 in the West Lancashire List, are to be found. As this limestone area 

 is so rich in land species, it will be as well to define it more exactly. It 

 includes Grange-over-San ds, Arnside, Silverdale, the Yealands, War- 

 ton, Burton-in-Kendal, Milnthorpe, and intermediate villages. Grange 

 is separated from the other districts by the broad estuary of the Kent. 

 Mr. Standen's records for this locality are now well known, and the 

 repetition of them in the following pages may seem to some super- 

 fluous; but while this may be so, it is necessary, in order to preserve a 

 complete sequence, to consider the district as a whole. 



Kirkby Lonsdale can perhaps be looked upon as a connecting link 

 with Ingleton and the Craven Highlands, and here there is a some- 

 what isolated outcrop of limestone. Through this the river Lune has 

 cut a narrow defile, which is spanned by the well-known Devil's 

 Bridge. This is the only locality for Azeca tridens and one of the 

 few for Vertigo alpestris. 



To return to the Lancaster area : To the east of the county 

 town are the Wyresdale and Littledale Fells. These desolate moors, 

 covered with gorse and heather, must form a very definite barrier to 

 dispersal. Five species only have been taken at altitudes of about 



