PHYLETIC BRANCHES AMONG THE VERTEBRATES 175 



Thus limited by the small progress in palaeonto- 

 logical exploration to the study of the Tertiary 

 mammals alone, we may yet point out even now 

 some phyletic branches, the real evolution of which 

 continues over a notable part of Tertiary times. 

 To our knowledge, one of the longest branches it is 

 possible to reconstruct with certainty at the present 

 time is that of the family of Anihracoiherides. The 

 theoretical importance of this demonstration in- 

 duces me to enter here into a few details. 



The Anthracotherids belong to the Sullian Para- 

 digits, that is to say, to the Ungulates with an even 

 number of digits bordering on the Swine, with 

 whom they have many points of structure in 

 common. They are distinguished from the Suidse by 

 the profile of their skulls, which are lower behind, less 

 raised in the occipital region, and by the less buno- 

 dontal type of structure of their molars that is to 

 say, these teeth are formed of denticles more or less 

 compressed into half- crescents, instead of being 

 almost regular cones ; this last type, which is 

 that of the Swine, seems adapted to a more com- 

 pletely omnivorous diet. This family of the An- 

 thracotherids, which predominates in a maximum 

 degree in the Oligocene epoch, is easily separated 

 into a fairly large number of phyletic branches, of 

 which the three principal are : (1) the Anthraco- 

 therium branch, characterized by a moderately 

 long skull, and by molars having five short and 

 conical tubercules (type Brachybunodont) ; (2) the 

 Brachyodus branch, with a not very long skull, 

 and molars having five short tubercules, half- 

 crescent shaped (type Brachyselenodont) ; (3) 



