546 HISTORY OF THE HUMAN BODY 



Sub-Order i. Suina (Elotherium; pigs; peccaries; 

 hippopotamus). 



Sub-Order 2. Tylopoda (Orcodon; camel; llama). 



Sub-Order 3. Anthracotherioidea ( Anthrac other i- 

 um). 



Sub-Order 4. Dichobunoidea (Dichobune ; Ano- 

 plotherium). 



Sub-Order 5. Traguloidea (Tragulus, several 

 small species in E. Indies). 



Sub-Order 6. Pecora (deer; sheep; cattle; gi- 

 raffe). 



[The arrangement of animal groups in the form of a 

 list, in which they follow one another in a single series, 

 is seldom more unsatisfactory than it is in the .case of 

 mammals. The inadequacy of this method in expressing 

 the true relationships is seen if the list be compared with 

 the phylogenetic tree given in Chapter II. (p. 36). There 

 are several distinct stems to be followed and the order 

 in which they are taken in a list is largely a matter of 

 preference. Here the attempt is made to proceed from 

 the generalized to the more specialized ones, and thus 

 the main stem of the Insectivora is taken first ; then that 

 of the Primates, and lastly the complex and highly spe- 

 cialized branch leading to the carnivore and ungulate 

 Orders. This arrangement has the advantage of empha- 

 sizing the primitive and rather generalized structure of 

 the Primates as compared with the groups just men- 

 tioned, a comparison entirely lost sight of by the usual 

 arrangement, which places the apes and man at the top. 

 If the arrangement be made solely on the basis of the 

 development of the nervous system there can be no ques- 

 tion of the rightfulness of this position; but if all the 

 systems be taken into consideration, and especially the 

 bones, muscles and teeth, which in other groups form the 

 principal criteria for the purpose of classification, the 

 Primates are found to have retained a larger number of 

 primitive characters than any other placental group with 

 the exception of the Insectivora, Rodentia, and Edentata, 

 and thus to stand far lower in the scale of specialisation 

 than the manifold descendants of the Creodonta and 

 Condylarthra. 



The arrangement of the subdivisions of the Primates 

 given above is a conservative one, and will accord with 

 the most of the literature on the subject. Certain im- 

 portant modifications have, however, been recently pro- 



