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CLASSIFICATION. 



General distribution of the Animal Kingdom into Four 

 Great Divisions. 



First Great Division. Animdlia Vertebrata — Vertebrated 



Animals. 



The interior skeleton forming the solid frame-work of the 

 body. Nervous system composed, besides the ganglions and 

 the nerves, of a brain and a spinal marrow situated above the 

 digestive tube and inclosed in the cavity of the cranium and 

 the vertebral canal. Blood red; heart muscular, with at 

 least two cavities. Respiration generally aerial and pulmo- 

 nary; sometimes aquatic, being effected by means of bran- 

 chiae. Mouth with two jaws placed one above or at least 

 before the other. Organs of sense to the number of five, and 

 distinct ; four are lodged in the cavities of the head. Form 

 of the body symmetrical; never more than two pairs of 

 limbs. 



Subdivision of the Vertebrata into Four Classes. 



FIRST CLASS. MAMMALIA. 



Viviparous ; having mammae and hair ; blood warm ; cir- 

 culation double and complete ; heart with four cavities ; res- 

 piration pulmonary, and simple. 



SECOND CLASS. BIRDS. 



Oviparous ; having feathers ; blood warm ; circulation 

 double and complete ; heart with four cavities ; respiration 

 pulmonary, and double. 



THIRD CLASS. REPTILES. 



Oviparous ; skin naked or furnished with scales ; blood 



