CHAP. VIII.] TEIASSIC PERIOD. 125 



up of the Magnesian Limestone sea. It is certain that the 

 general elevation was accompanied by differential move- 

 ments producing areas of comparative depression and 

 elevation ; thus a further uplift of the Pennine range took 

 place, and the Dyassic beds on either side received a slight 

 tilt, so that the lower beds of the Trias were laid down 

 across their edges, and overstepped them on to the Car- 

 boniferous rocks. Consequently that beds of intermediate 

 age should exist beneath the Trias to the eastward is only 

 what might have been expected. 1 



That the continued upheaval caused a great alteration 

 in the physical conditions of the European region is evident 

 from the great changes which took place in its inhabitants. 

 The Dyassic forms of life, which were mostly survivals of 

 Carboniferous forms, were completely exterminated and re- 

 placed by a different fauna and flora. Among plants new 

 genera of ferns and conifers appeared, Cycads began to 

 flourish, and Equisetum replaces the Carboniferous and 

 Permian Catamites. The fish and reptiles which inhabited 

 Triassic waters all, except Palceoniscus, belong to new and 

 distinct genera ; crocodiles and Dinosaurs now first appear, 

 and before the end of the period a marsupial mammal 

 made its way into the British area. 



1 Professor A. H. Green's review of Lebour's " Geology of Northum- 

 berland and Durham " (in " Nature," July 28, 1887) came to hand after 

 this chapter was written. He takes exactly the same view of the 

 Middlesbrough beds, and observes "It seems likely that toward the 

 end of the Permian period unequal subsidence produced hereabouts a 

 depression in the bed of the water; that as now happens elsewhere 

 under similar conditions, the Permian lake became largely laid dry, so 

 that the water remained only in this and perhaps other similar basins ; 

 and that from the highly concentrated solutions which remained in 

 these lakelets local deposits of a strongly chemical character were pre- 

 cipitated." To this I will only add that the " Gypseous Shales " of the 

 Carlisle basin may belong to the same period of transition, and may 

 have been formed in a similarly limited basin, for some geologists class 

 them with the Trias and some with the Dyassic rocks. 



