OUB BODILY FRAME. 33 



the monotremes. There are, likewise, other anatomical 

 features, particularly the higher development of the 

 brain and the absence of the marsupial bone, which 

 raise the placentals above all their implacental 

 ancestors. In all these important particulars man is 

 a tine placental. 



The very varied sub-class of the placentals has been 

 recently subdivided into a great number of orders ; 

 they are usually put at from ten to sixteen, but when 

 we include the important extinct forms which have 

 been recently discovered the number runs up to from 

 twenty to twenty- six. In order to facilitate the study 

 of these numerous orders, and to obtain a deeper 

 insight into their kindred construction, it is very 

 useful to form them into great natural groups, which 

 I have called " legions." In my latest attempt 1 to 

 arrange the advanced system of placentals in phylo- 

 genetic order I have substituted eight of these legions 

 for the twenty-six orders, and shown that these may 

 be reduced to four main groups. These, in turn, are 

 traceable to one common ancestral group of all the 

 placentals, their fossil ancestors, the prochoriata of 

 the Cretaceous period. These are directly connected 

 with the marsupial ancestors of the Jurassic period. 

 We will only specify here, as the most important 

 living representatives of these four main groups, the 

 rodentia, the ungulata, the carnivora, and the primates. 

 To the legion of the primates belong the prosimiae 

 (half-apes), the simise (real apes), and man. All the 

 members of these three orders agree in many important 

 features, and are at the same time distinguished by 

 these features from the other twenty- three orders of 

 placentals. They are especially conspicuous for the 



1 SystematUche Phylogenie, 1896, part iii., pp. 490, 494, and 496. 



D 



