FIEST SUB-KINGDOM. 



TEBTEBEATA. 



The four great Classes of Cuvier, comprising this, Province of the 

 Animal Kingdom, have in common a general type of structure, clearly 

 recognizable in all the members of the series. The grand characteris- 

 tic is an interior jointed skeleton, made up of vertebras, which with their 

 processes form two cavities — the upper enclosing the great nervous 

 cord, the lower containing the viscera. 



The history of Mammals, Birds, Reptiles and Fishes, as a sub-king- 

 dom, reaches back to the Upper Silurian Period. Their fossil bones 

 and teeth, usually in a fragmentary state, have been found in every 

 stage of alteration, from their present gelatinous state to that of com- 

 plete petrifaction, and demonstrate the existence of numerous tribes of 

 highly organized beings in the primeval age of the world, and the contin- 

 uance of the same type of organization to the present day. The earliest 

 evidence of a vertebrate animal, is of the cold-blooded, water-breathing 

 class. The vertebrate type, however, did not start from the inferior 

 Fishes, but from the higher forms — the Ganoids and Selachians; the 

 species now swarming in river, lake and ocean, did not come into exist- 

 ence until the Cretaceous Period. Reptiles were introduced in the 

 Carboniferous — first Amphibious, then the typical forms. In the Rep- 

 tilian Age come the first of Birds, and the first of Marsupials. The 

 true Birds and Mammals had their full expansion in the Tertiary. 

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