﻿446 MR. R. H. RASTALL ON THE [Aug. I905, 



The Terebratula-~Be& consists of 2 feet or so of dark-brown 

 sandstone, full of fossils, which are, however, very difficult to extract 

 in a perfect state. By far the most abundant is Tevebvatula tri- 

 lineata, but the following are also recorded from this bed 1 : — 



Terebratula submaxillata. j Trigonia Eamsayi. 



Bhynchonella cynocephala. \ 



Belemnites inornatus. 

 Gresslya peregrina. [ Belemnites irregularis. 



Above this comes a brown shaly bed, about 1 foot thick, con- 

 taining very few fossils. I have obtained only an internal cast of 

 an indeterminable Trigonia. This bed is noteworthy for the very 

 large amount of mica which it contains. All the beds of the 

 Blea Wyke Series are markedly micaceous, but this is the most 

 conspicuous of all in that respect. The great abundance of detrital 

 mica may possibly throw some light on the source of the material 

 of which these rocks are composed. 



This shaly bed is succeeded by some 25 feet of greenish-yellow 

 sandstone, usually classed with the Dogger ; but, for reasons 

 which will appear later, I have drawn the base-line of the Dogger 

 at this horizon. Lithologically, this sandstone is very similar to 

 the Yellow Beds below it, and contains abundant pebbles. 



Perhaps the most noticeable feature of these Yellow Beds is the 

 occurrence of numerous bands of black nodules or 

 pebbles, which occur at several different horizons, as well as 

 scattered at intervals throughout the whole series. The origin 

 and nature of these pebbles has given rise to much discussion, 

 without any very satisfactory conclusion. It is obvious that many 

 of them are rolled fragments of fossils, and some are clearly recog- 

 nizable as Liassic ammonites. These pebbles have a very wide 

 distribution, being found at most of the sections where the junction 

 of Lias and Oolite is displayed. They vary considerably in size at 

 different localities, but at Blea Wyke they are generally small, 

 not often exceeding 1 inch in diameter. It is significant that they 

 increase in number towards the top of the passage-beds, in which 

 other indications point to a gradual shallowing of the water, or 

 approach to a shore-line. 



(4) The Dogger. 



The beds which are here taken to be the equivalent of the base- 

 ment-bed of the Oolite, or Dogger, of other sections in the northern 

 part of the district, consist of two parts, thus : — 



Thickness in feet. 



"Ferruginous sandstone, with scattered pebbles , 10 



The Werincea-Bed . li 



1 0. Fox Strangways, 'The Jurassic Rocks of Britain: vol. i — Yorkshire 

 Mem. Geol. Surv. 1892, p. 153. 



