LATER LIFE ON THE EAKTH 49 



were not common until the Cretaceous. The first 

 skates are also Jurassic. 



The Triassic and Jurassic forests consisted chiefly 

 of short-stemmed cycads and pines, with an under- 

 growth of ferns. There is little or no advance on 

 the flora of the Deutozoic era, the difference being 

 chiefly due to the absence of the large Equisetacese 

 and Lycopodiacese of the Carboniferous, combined 

 with a great increase of Gymnosperms. In the 

 Cretaceous period, however, we find a great im- 

 provement ; for here we have the dawn of the modern 

 flora. In addition to palm trees and other Monoco- 

 tyledons, Dicotyledons are abundant in the lower 

 Cretaceous of North America and of Portugal ; 

 and in the upper Cretaceous this flora spread 

 through Europe into Greenland, even as far as 

 81 45' N. 



Part of the early Mesozoic flora of Europe is 

 thought by some naturalists to have originated in 

 the southern hemisphere, and to have migrated 

 northwards from Australia through India. But 

 there appears to be no good evidence of this, except 

 with the genus Glossopteris , which is Permo-car- 

 boniferous in Australia, and associated with 

 Cordiates, Cyclostigma, Lepidodendron, Calamites 

 and Sphenopteris. Among the vegetation insects 

 were common. In addition to the Orthoptera and 

 Neuroptera, already noticed, we now have beetles, 

 cicadas, flies, and ants. 



The Mesozoic has been well called the age of 

 reptiles, so numerous and varied were they. A very 

 short glance at them will, however, be sufficient ; 



