54 LINKS WITH THE PAST [ch. 



places in the Inner Hebrides. Many of the Jurassic 

 strata contain only marine shells, and corals are 

 occasionally abundant, though in the lower members 

 of the system in the cliflfs near Lyme Regis and at 

 Whitby fossil plants are ftiirly common. It is, how- 

 ever, from the middle Jurassic beds, in the cliffs 

 between Whitby and Scarborough, and in some 

 inland quarries in East Yorkshire, that we have 

 obtained the richest Jurassic flora. Rivers from a 

 northern land laden with sediment and carrying drift- 

 wood, leaves and other plant fragments, deposited 

 their burden in an estuary which occupied the eastern 

 edge of Yorkshire. Sedimentary rocks laid down 

 towards the close of the Jurassic period in the island 

 of Portland in the south and on the Sutherland coast 

 in the north have furnished valuable records of 

 plant-life. 



The passage from the Jurassic to the underlying 

 Triassic system is formed by some shales and lime- 

 stones in South Wales containing remains of fish and 

 other marine organisms. These so-called Rhaetic 

 beds are poorly represented in the British area, but 

 on the continent of Europe and in other regions the 

 sediments of this age bulk much more largely and 

 have yielded a rich collection of plants. The rocks 

 of the upper division of the Triassic system, as seen 

 in the Midlands, point to the prevalence of desert 

 conditions ; and in the grooved sand-polished surfaces 



