The Artiodactyla. 1091 
tained, it was found to be artiodactyle, as suspected by Kowalev- 
sky. One species, L. splendens, has been found in the Middle 
Miocene of Western Europe. Hippohyus C. and F. is known from 
the Indian Siwaliks. A genus of probable affinities to it, founded 
on teeth only from Asiatic localities, is the Sanitherium of Schlag- 
intweit. Some of the extinct species of Sus were of larger size than 
the existing hog, as the S. giganteus of the French Miocene, and the 
S. erymanthius of Pikermi, Greece. The S. silvanius Hodgson, a 
recent Indian species, is not larger than a small dog. 
The phylogeny of these two bunodont families is nearly as follows, 
although the absence of intermediate types renders the final deter- 
mination as yet impracticable. The main features may be how- 
ever foreshadowed. The most generalized form is Paleocheerus, 
since its dentition is in all respects the most simple, while it pre- 
serves the full number of teeth. An unknown form resembling it, 
but with well-developed canine teeth, may have readily given origin 
to the Dicotyline line on the one side, and Sus and its immediate 
allies on the other. Babirussa is another derivative from the same 
centre. Phacochcrus may have come from some ally of Sus, since 
it carries to a great extreme the peculiarities of the latter genus. 
The ancestry of Hippopotamus is less easily determined. Its im- 
perfect distal metapodial keels, which only exist on the posterior 
face of the condyle, bespeak for it an ancient ancestor. Its molar 
type is merely a complication of the quadritubercular, while the 
characters of its canines are an exaggeration of those of the prim- 
itive forms already mentioned. Several other genera, as Dicotyles 
and Sus, display. the decumbent incisors which prepare the way for 
the remarkable straight digging incisors of Hippopotamus. The 
genus Hexaprotodon eases the passage backwards. These relations 
may be expressed as follows :— 
Cheeropsis. Phacocheerus. Platygonus. 
Hippo, otamus, Dicotyles, Cheenohyus. 
Hexaprotodon. Babirussa. Sus. Bothrolabis. 
f 
f 
\ vs vai eal 
\ J e 
\ PA P A port ae ; 
x \ ff J A 
* 
Hyotherium, 
