INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
SIWALIK SELENODONT SUINA, ETC. 
By R. LYDEKKER, B.A., F.Z.S., 
GEOLOGICAL SURVEY OF INDIA. 
(WITH PLATES XXIII. to XXV.) 
Order: UNGULATA; Division: ARTIODACTYLA ; 
Section: SUINA SELENODONTIA. 
Introductory. — The extensive and important group of pig-like Artiodactyle 
Ungulata, commonly classed together under the head of Suina, may conveniently 
be divided into two subordinate groups, distinguished from each other by the 
structure of their molar teeth. The first of these groups may be termed the 
Bunodontia , 1 and is characterised by having the cusps, or columns, on the grinding 
surfaces of the upper molar teeth arranged either in an irregular manner, as in 
the common pig, or with a more or less distinct tendency to the production of 
larger columns at the four angles of the crown as in Tetraconodon 2 : this group 
comprehends the hippopotamus, and all living pig-like animals, as well as the 
extinct Hyotherium, Entelodon ( Elotlierium ), and their allies. The second group, 
forming the main subject of the present memoir, may be termed the Suina 
Selenodontia , 3 and is characterised by the upper molars having their inner pair 
of cusps, or columns, of a more or less, distinctly crescent shape. This second 
group is now totally extinct, and is represented by Ghoeropotamus , Eyopotamus, 
Or cod on, and a host of kindred forms. As is nearly always the case in a 
large group of animals, there is always a difficulty in referring all . the forms 
to their respective sub-division, and this is exemplified in genera like 
Chceropotamus, and some species of Anthracotherium , which, though belonging 
to the selenodont group, yet afford an easy transition from its most typical 
members, like Oreodon, to some of the more specialized of the bunodont group, 
like Tetraconodon. 
1 From bounos, a hillock, and odous, a tooth. 
2 Vid. sup., Vol. I., pi. X. 
3 From seleite, the moon, 
