128 



JJ^. D. Lfiufj — Zone of HopJitcx infrrynptxs 



In these specimens tliere is a very thin layer of clay varying fronv 

 about i inch to an almost imperceptible thickness, of paler coloiu* 

 tban the clay below. The upper boundary of this layer is the 

 jagged, wavy, but sharply defined line already mentioned, and the 

 lower boundary a much less clearly defined though comparatively 

 straight line. This pale layer is described from dried specimens, and 

 it was not seen whether it was noticeable when they were freshly cut. 



Fig. 3. — Specimen SH0^VING the Junction between the Selhornian 

 AND l.iAs ON Black Yen, natvral size. 



1. Selboruiau Loam. 



2. Pale band at tlie top of Lias Clay. 



3. Lias Clay. 



The pebble bed is not easy to see, as the pebbles are very incon- 

 spicuous, but its presence is easih'^ detected by the grating of the 

 pebbles against the trowel when the bed is dug into. 



The pebbles vary in size from that of a pigeon's egg to that of 

 coarse sand. They are mostly subangular, but some are well 

 rounded, and are nearly all of silica in various foi'ms. Vein quartz 

 is the chief of these, forming the largest pebbles. Others are of 

 brown chert with a very smooth pale-green altered surface. A few 

 were of white limestone and of black grit. A few fragments of 

 Belemnite were also found. The constituents of a washed sample 

 are given in the Survey Memoir.' 



The matrix in which the pebbles lie is a loam of dark greenish 

 colour, the darkness being due to the presence of blue clay, and the 

 green to that of a small quantity of glauconite. The loam alsO' 

 contains a little mica. The bed becomes sandier towards the top, 

 gradually passing into the next bed. 



No fossils vv^ere found in this bed, nor in bed 2. 



Bed 2. This is like bed 1. but sandier, and consequently lighter 

 in colour. Yellow patches of comparatively pure sand occur in it. 



A few feet up this bed is overlain by a mass of yellow sand fallen 

 from the higher beds, upon which rests the soil of the cliff slope 

 above. This slope is verj' slight, and is marked by a tract of over- 

 grown land from 50 to 100 yards wide, backed by a cliff of yellow 



^ Jukes-Browuo: loc. cit., p. l.Si). 



