426 



MESOZOIC ERA— AGE OF REPTILES. 



ground, covered with trees and other vegetation peculiar to that time, 

 the decaying leaves of which accumulated as a rich and thick vegetable 



Fig. 628.— Section in Cliff east of Lul- 

 worth Cove: a, Dirt-bed. 



Fig. 629.— Section in the Isle of Portland: 

 a, Dirt-bed. 



Fig. 630.— Zamia spiralis, a Living Cycad of Australia. 



mold. 3. It became flooded with fresh water, and the trees therefore 

 died and rotted to stumps. 4. The whole ground, with its stumps and 

 logs, became covered with mud, which hardened into slates. 5. Fi- 

 nally, the whole was 

 raised into high land, 

 and in the first figure 

 (Fig. 628) tilted at a 

 considerable angle. 



Thus, we have here 

 not only an old forest- 

 ground with its vegeta- 

 ble mold, but also the 

 stumps and logs of the 

 trees which grew there, 

 still in place ; and closer 

 examination easily detects the kinds of trees which grew in the forest. 

 They are Cycads and Conifers (Figs. 630, 631 and 635-638). Still fur- 

 ther, there is good reason to believe that the remains of some of the 

 animals which roamed these forests have also been found. Of these 

 we will speak in their proper place. 



Plants. 



Although the conditions under which coal was accumulated were 

 probably similar in all geological periods, yet the kinds of plants out of 

 which the coal was made varied. As already seen, the principal coal- 

 plants of the Carboniferous period were vascular Cryptogams. On the 

 contrary, the principal coal-plants of the Jurassic period were Ferns, 

 Cycads, and Conifers. The Jurassic may be called the age of Gym- 

 nosperms, as the Carboniferous was the age of Acrogens. The Gym- 

 nosperms, especially the family of Cycads, reached here their highest 

 development. This is shown in diagram on page 283. The leaves 

 (Fig. 631) and short stems of Cycas and Zamia (Fig. 638) are found 



