THE PEE-ADAMITE EARTH. 



Synopsis of the animal kingdom. 439. Outlines of land and water. 

 440. Rich, vegetation. 441. Great extent of land in Russia, South 

 America, and India termination of the period. SIXTH CRETACEOUS 

 PERIOD. 442. Mineral character of the stage. 443. Synopsis of 

 the animal kingdom. 



400. THE Cretaceous age is zoologically distinguished from the 

 Jurassic by the absence of upwards of 180 generic forms which, 

 existed in the previous age, and from the succeeding age by the 

 absence of upwards of 500 genera not created until the succeeding 

 one these 500 genera consisting of 24 orders of animals, as 

 follows : 



Mammifers . 



Birds 



Beptiles 



Fishes . 



Crustacea 



Insects . 



Mollusca and Radiata 



Orders. 

 . 11 

 5 



Total 



24 



401. During this age about 270 genera were created, but it is 

 by the specific forms that its fauna can be more distinctly cha- 

 racterised. These consisted of about 5000 species, of which, about 

 700 belonged to the vertebrata and annulata. The manner in 

 which the species of mollusca and radiata are distributed among 

 the stages is as follows : 



The same species being repeated in the second column, a corre- 

 sponding deduction from the total number of common species must 

 be made, which will reduce the actual number of such common 

 species to 21, being only a half per cent, of the total number. 



402. From a general analysis of the facts, the following 

 conclusions may be inferred : 



1 That there existed in the Cretaceous age above 5000 species 

 of animals altogether distinct from those of the preceding and 

 98 



