263 



HOLOCENE MOLLUSCA NEAR GREAT MITTON, 

 WEST YORKSHIRE 



]5y J. VVILFRIl) JACKSON, F.G.S. 



(l\cad Ijcfurc the Society, Koveiiilier iitli, ii;oS). 



Thk Holocene deposits of the Ribble valley, though in places faiily 

 extensive, appear to have hitherto l^een neglected. In fact one might 

 say the same regarding the recent niollusca of this corner of Yorks , 

 as, with the exception of three excursions made by the Yorkshire 

 Naturalists' Union, when on each occasion Mr. W. Denison Roebuck 

 appears to have been the sole conchologist of the party, no systematic 

 attempt has been made to study the mollusca, although the adjacent 

 ^Vhalley district has been pretty well worked. 



Whilst traversing the district some weeks ago I devoted some time 

 to an examination of the banks of the river and succeeded in obtaining 

 a fairly respectable list of shells. 



The Ribble, after flowing through the narrow Carboniferous Lime- 

 stone gorge between Gisburn and Sawley Abbey, continues its S.^V. 

 course through the limestone districts of Chatburn and Clitheroe, 

 where are extensive alluvial deposits and river terraces, especially 

 north of Chatburn; thence through the sandstones and marls of 

 Permian age below ^Vaddow Hall and over the "shales-with-lime- 

 stones," past Great Mitton, a little below which place it is joined by 

 the River Hodder, draining the Grit Fells on the west. l'"rom 

 Waddow Hall to the junction of the Hodder are further alluvial Mats, 

 especially on the Yorkshire side of the river. 



Both above and below Mitton bridge, which spans the Ribble here, 

 the alluvium contains land and freshwater shells more or less 

 abundantly. 



The right, or Yorkshire, bank of the river varies somewhat in height, 

 being on the average about si.x feet high, the ground gradually 

 increasing in height as it recedes from the river. The underlying 

 rock is only seen in one or two places near the bridge where beds of 

 sandstone occur, dipping at an angle of about 20°. 



Though common all along the bank and scattered through the 

 alluvium from bottom to top, the shells appear to be specially 

 abundant at a point about a third of a mile down from the bridge, 

 where the river takes a sharp turn to the right opposite a high cliff of 

 Boulder Clay situated on the Lancashire side. Here the bank slopes 

 more gradually down to the water's edge and is much burrowed into 

 by rabbits. Numerous shells have thus been thrown up and lie 



