1873.] 



Osteology of the Hyopotamidre. 



151 



in finding for the two groups convenient names ; and by his suggestion I 

 should call the Paridigitata with crescentic teeth Par. selenodonta, and 

 those with tubercular teeth Par. bunodonta. 



To the first group would belong all the ancient and Hying Paridigitata 

 having crescentic teeth, as the Anoploiherium, Xiphodon, Dichobune, An- 

 thracotherium, Bothriodon, Hyopotamus, Rhag either mm, and the living Bn- 

 minantia. 



The second would embrace all the Suina, Hippopotamina, and Entelodon. 



Each one of these two groups may be again subdivided on the prin- 

 ciples adopted in this paper. 



By such division, we shall gain the advantage of having the Paridigitata 

 arranged into two distinct lines of descent ; every new discovered form 

 will at once have its place along one of the lines, and the true pedigree of 

 both will be ascertained much sooner and with greater accuracy. Whilst 

 now making no such clear division, palaeontologists, in projecting their 

 genealogical tables, mix both groups together; and, according to the 

 need of the moment, they place forms belonging to one line of descent 

 in the other, and vice versa. Thus, for instance, all the Hyopotamoids 

 and Anthracoiherium are constantly moved about from one line to the 

 other *, while their true place is along the line of Selenodont Paridigitata; 

 and they have nothing to do with the Bunodont Suina, although groups 

 quite parallel with them may be found on the descending line of Bunodont 

 Paridigitata. Such parallelism, however, does not imply direct links 



Divergence of Selenodont 

 and Bunodont Paridigitata. 



□ 



□ 



□ 



Dicotyles. Hyomoschus. 



along parallels drawn across both diverging and descending lines ; the 

 links are to be found only by climbing along the ascending lines to near 

 the point of separation. For instance, Dicotyles and Hyomoschus occupy 

 analogous positions ; but there is no link between them along the dotted 

 parallel. Links will be found only by going up to the point near their 

 separation. 



There are, no doubt, to be found around the points of divergence many 

 forms of which it is difficult to say whether their teeth are tubercular or 



* In fact described constantly as Suina. See Gervais, ' Paleontologie de France.' 



