186 NEOZOIC TIME. [CHAP. X. 



Triassic deserts were converted into fertile and forest-clad 

 districts. The land of Vectian time was doubtless similar 

 in climate and aspect to that of Wealden time, and the 

 plants and creatures which inhabited the country were the 

 direct descendants of those that lived in the Purbeck and 

 Wealden periods. 



The geography of the British area had now become 

 similar to what it was at the close of the Portlandian epoch. 

 There were two gulfs, one on the south, in which the Ather- 

 field Clay and Walpen Sands were accumulated, and one to 

 the north-east, in which the middle part of the Speeton 

 Clay was contemporaneously deposited. For a certain time 

 after the first invasion of the Wealden lake the land seems 

 to have been nearly stationary, so that this basin was 

 gradually silted up, and shallow- water conditions prevailed 

 till further subsidence took place. Thus in Oxfordshire 

 and in Normandy (Pay du Bray), outside the limits of the 

 marine Lower Vectian Beds, we find freshwater deposits 

 similar to those of the Wealden, but probably of Vectian 

 age. 



Marine erosion, however, was active, and, aided by further 

 subsidence, the sea spread farther and farther over the 

 ground which separated the two gulfs, till at length the 

 waves effected a junction across the lowest part of the 

 intervening isthmus and invaded the lacustrine area, which 

 seems at this time to have existed on the isthmus, and in 

 which the Shotover Sands were formed. The communica- 

 tion thus established became a narrow strait or channel, 

 through which a strong current ran from the northern to 

 the southern sea (see p. 169). This channel doubtless in- 

 creased in width, but there is no evidence that the sea had 

 encroached very far either on the eastern or western land 

 before the formation of the G-ault, which overlaps the Vec- 

 tian sands in both directions. Its western coast evidently 

 consisted of Upper Jurassic rocks, and it is probable that 



