122 THE MIDDLE PAST. 



These and other distinctions, upon which our limits will 

 not permit us to dwell, stamp the palaeozoic as a life-period 

 widely different from that of the mesozoic, and yet there 

 was no break, no discontinuity in the great evolution of 

 vitality. As the life of one system runs imperceptibly into 

 that of another, and the two have always some forms in 

 common ; so the palaeozoic runs into the mesozoic, and it 

 is only when viewed as a whole, and at a sufficient distance, 

 that its distinctive characters stand out in bold and peculiar 

 relief. So in like manner we shall find it with the meso- 

 zoic life-period, when we have reviewed the forms of its 

 triassic, oolitic, and cretaceous systems. It has a facies 

 peculiar to itself, and though approaching in some of its 

 features, yet as a whole unmistakably different from the 

 facies of the cainozoic period, which is now running its 

 course, and bearing us along with it. 



And first, we turn to the Trias or upper new red sand- 

 stone, with its " triple" series of various coloured sandstones, 

 shelly limestones, and saliferous and gypseous shales. These 

 party-coloured deposits, in which ferruginous tints predo- 

 minate, are clearly the sediments of circumscribed oceanic 

 areas areas which, in the northern hemisphere at least, 

 were of no great depth, and subjected to repeated elevatory 

 and depressing movements. This new arrangement of sea 

 and land, accompanied by no gigantic rivers or estuaries, 

 and apparently by a somewhat arid climate, is characterised 

 by a numerical as well as specific paucity of life a paucity 

 which is greatly aggravated by the unsuitable nature of 

 the sandstones and marls for the preservation of organic 

 remains. Physiologically, however, the forms are still on 

 the advance ; cycads and conifers are more decided in their 

 characters ; brachiopods diminish, and true bivalves in- 

 crease ; cold-blooded air-breathers become more numerous, 



