Upper Lias. 1 7 1 



posed. In Yorkshire, however, on the sea-cliffs near 

 Staithes, the stratigraphical relations of the strata are 

 perfectly clear, and it is evident that there is no line of 

 demarcation between them, and through about 15 feet 

 of strata, including some of the well-known beds of 

 ironstone, fossils common to both occur, one of the 

 most conspicuous of which is Pecten cequivalvis. 



THE UPPER LIAS CLAY plays a comparatively un- 

 important part in the physical geology of England. In 

 Gloucestershire it first begins to appear near Bath, but 

 so thin, that it is impossible to represent it on maps of the 

 1-inch to a mile scale. About Wotton-under-Edge it 

 begins to get more definite, and from thence, in a 

 narrow strip between the Marlstone rock, and the sands 

 beneath the Inferior Oolite, it runs northward by 

 Dursley, Stroud, Pains wick, and Chipping Camden, and 

 following all the contours of the Oolitic escarpment, 

 looks out upon the great plain of Lias, in the broad 

 valley of the Severn, or winds about among the intricate 

 system of minor valleys that lie between Minchin- 

 Hampton and Chipping Camden, and between Burford 

 and Banbury. In this progress, gradually increasing in 

 thickness, it forms great tracts of the clay lands in 

 Northamptonshire, between Great Brington and Arth- 

 ington, and in the neighbourhood of Uppingham and 

 Oakham in Rutland, while further north, the clay runs 

 in a long narrow strip, still overlying the Marlstone, 

 into Yorkshire, where it is finely exposed in the sea- 

 cliffs near Whitby, and where in old times great excava- 

 tions were made for the extraction of shale, and the 

 manufacture of alum. 



Taken as a whole, the Upper Lias is a stiff dark 

 blue clay, with occasional layers of limestone often 

 nodular, containing many Belemnites, Ammonites, and 



