Ch. xyiilj 



WEALDEIST FOSSILS. 



263 



Fig. 309. 



Fig. 810. 



Corbula alata, Fitton. Magnified. 



In brackish-water beds of the Hastings 



Sands, Punfield Bay. 



TTnio Valdensis, Mant 



Isle of "Wight and Dorsetshire ; in the lovrer beds 



of the Hastings Sands. 



becomes purely marine, the species being for the most part peculiar, but 

 several of them well-known Lower Greensand fossils, among which Am- 

 monites Deshayesii may be mentioned. These facta 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 sand- 

 stone (see fig. 311). 



Fig. 311. 



Underside of slab of sandstone about one yard in diameter. 

 StamiDerham, Sussex. 



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

 merable traces of a fossil vegetable, apparently Sphenopteris, the stems 

 and branches of which are disposed as if the plants were standing 

 erect on the spot where they originally grew, the sand having been 

 gently deposited upon and around them ; and similar appearances 



