350 



WEALDEN FOSSILS. 



[Oh. XVIII. 



some places this bed becomes purely marine, the species being for the 

 most part peculiar, but several of them well-known Lower Greensand 



Fig. 344. 



Fig. 345. 



Corbula alata, Fitton. Magnified. 

 In brackish-water beds of the Hast- 

 ings Sands, Punfield Bay. 



TTnio Valdensis, Mant. 



Isle of Wight and Dorsetshire ; in the lower beds 



of the Hastings Sands. 



fossils, among which. Ammonites Deshayesii may be mentioned. These 

 facts show how closely related were the faunas of the Wealden and 

 Cretaceous periods. 



At different heights in the Hastings Sand, we find again and again 

 slabs of sandstone with a strong ripple-mark, and between these slabs 

 beds of clay many yards thick. In some places, as at Stammerham, 

 near Horsham, there are indications of this clay having been exposed 

 so as to dry and crack before the next layer was thrown down upon 

 it. The open cracks in the clay have served as moulds, of which casts 

 have been taken in relief, and which are, therefore, seen on the lower 

 surface of the sandstone (see fig. 346). 



Fig. 346. 



Underside 



slab of sandstone about one yard in diameter. 

 Stammerham, Sussex. 



Near the same place a reddish sandstone occurs in which are in- 

 numerable traces of a fossil vegetable, apparently Sjphenqpteris, the 

 stems and branches of which are disposed as if the plants were stand- 



