GEOLOGY OF THE EAST CLIFF. 137 



At its base, and included in it, there 

 occurs a bed from two feet to three feet thick, 

 of a calcareous limestone, which is of two 

 qualities, one (the lower) called " blue " stone, 

 and the upper called "grey" stone. The 

 " blue " stone is, however, often absent. This 

 is regarded as valuable stone for road 

 metalling, and other purposes. At the 

 immediate base of this band there is a finely 

 laminated layer of cream-coloured sand 

 containing numerous remains of Hybodus, 

 chiefly the fin-spines, curved head-spines, and 

 teeth ; also of Crocodile, and Pterodactyl. The 

 layer might well be described as the Hybodus- 

 layer. At the top of this sandrock bed (the 

 19 feet bed) there is a surface layer of oxide 

 of iron, and ripple marks ; there is also a thin 

 band from a few inches to 12 inches thick, of 

 black carbonaceous sand, which, by percolation, 

 has stained the almost white sandrock below, a 

 dark hue. This band marks the commence- 

 ment of the Wadhurst Clays. The total 

 thickness here of Ashdown Sands is about 

 163 feet. 



