82 STRUCTURE OF THE VERTEBRATES 



Sub-order Lemuroidea. The lemurs were so named for their 

 nocturnal and ''ghostly" habits. The most primitive members 

 almost merge into the insectivores. Fossil lemurs were widely 

 distributed, but of the fifty existing species thirty-six are limi- 

 ted to Madagascar, the others being found in tropical Africa 

 and the Orient. The different species indicate the course of evo- 

 lution from the most primitive to the monkeys. 



Sub-order Anthropoidea. This sub-order carries the speciali- 

 zation of the nervous system and other body characters from 

 the primitive condition to man. In this group the teats are al- 

 ways in the pectoral region; the embryological structures of 

 nutrition (placenta) are similar; the skeleton shows the course 

 of evolution toward the upright position; and the nervous sys- 

 tem shows the steady advance from the lower monkeys to the 

 human. 



The South American monkeys are an early off-shoot from 

 the original stem, including the marmosets and the typical or- 

 gan grinder's monkey. They can be identified by the distance 

 between the nostrils, the septum being wide and the apertures 

 directed outward. Also, many of them are able to hang by their 

 prehensile tails. 



The Old World monkeys are more man-like, the nostrils be- 

 ing close together and separated by a narrow septum. The tail 

 is never prehensile. The teeth are thirty-two in number, the 

 dental formula being the same as in the higher families. The fam- 

 ily includes both the tailed monkeys and the apes, and members 

 are found in Africa, Southern Europe and Asia. The apes are 

 tlie most specialized of the primates, their dog-like faces and 

 vivid coloration making them unpleasantly ugly. These apes 

 and baboons have little relationship to the groups which gave 

 rise to the human family. 



The simian family includes the gibbons, which walk in an 

 almost upright position; the orang outans of the Malayan 

 regions; and the chimpanzees and gorillas of Africa. The last 

 two genera are the nearest relatives of man among living ani- 

 mals. The muscular system and the nervous system are almost 

 identical with those of man. In judging similarities between 

 groups the young should be studied, as older animals tend to 



