24 



GEOLOGY OF THE ISLE OF WIGHT. 



characters. Fossils are also comparatively scarce in Corapton 

 Bay. Dr. Fittou identified a " mass of brownish clay and sand " 

 which lies next above the Atherfield Clay, as the Lower Lobster 

 Bed, or the lowest part of the Crackers sub-division of Atherfield, 

 and a prominent portion in the lower part of the brown and red 

 grit as the Lower Gryphaea bed of Atherfield. 



The upper beds present a general resemblance to those which 

 form the upper part of Blackgang Chine, though they are very 

 much thinner, and contain none of the bands of sand-rock which 

 form so distinctive a feature in that chine. The abundance of 

 water strongly impregnated with sulphate of iron, which issues 

 from them, is a noticeable feature. As will be seen, the chalybeate 

 spring near Blackgang issues from the same beds. The annexed 

 wood-cut (Fig. 7) represents the general arrangement and 

 appearance of these upper beds in the cliflf. 



Atheiifield. 



The Lower Greensand here attains a greater development than 

 in any other part of the Isle of Wight, and has yielded a rich 

 suite of fossils. Its thickness has been variously estimated at 

 808 feet by Dr. Fitton, at 833 feet by Ibbetson and Forbes,* and 

 at 752 feet 11 inches by Mr, Simms. The description of it will 

 be taken from west to east, that is in ascending order of the 

 strata. 



The Atherjield Clay and Perna Bed. 



After leaving Compton Bay the Perna Bed is not seen again 

 till we reach Cowleaze Chine. It is here well exposed under the 



Fig. 8. 

 Perna Mulleti, Desh. 



* The thickness given by these authors is 843, hut the total ohtained hy adding 

 up the figures given iu their table is only 833. 



