MAMMALS. 189 



vertebra by a double prominence of the occipital bone. 

 The bones of the trunk are in the same relations to one 

 another as in man, and excepting the coccygeal ver- 

 tebrae are about the same in number. In a small group 

 the pelvis has supplementary bones, called epipubic or 

 marsupial bones, which terminate in front among the 

 muscles of the abdomen. The mammals belonging to 

 this group are also mostly characterized by the existence 

 of a sac, called the marsupial pouch, forming a fold in 

 the skin of the belly. These mammals, named didelphia, 

 bring into the world young ones whose development is 

 very little advanced, and who must, before they are able 

 to walk, remain for a considerable time suspended at the 

 teats of the mother, these teats being located in the 

 marsupial pouch. 



All the other mammals, having no marsupial pouch 

 and no marsupial bones, have been named monodelphia. 

 Here is the first basis for a classification. The other 

 characteristics are dependent on the number of limbs, 

 the manner of life, the arrangement of the extremities, 

 and the modifications of the dental system. 



These characters are indicated in the table on page 

 190. 



MAN. 



The organization of man places him at the head of 

 the great class mammalia. Anatomically, he is closely 

 related to the monkey, and this has led to his zoological 

 classification in the order Primates: the greatest ana- 

 tomical difference between man and the anthropoid apes 

 is found in the development of the brain. In the first 

 chapter we have indicated the principal features of man's 

 organism. 



The population of the globe has been classified by 



