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The Artiodactyla. 1093 
humerus is like Anoplotherium. The radiocarpal articulation is 
intermediate between that of hogs and ruminants. The unciform 
supports the lunar bone. The sacrum is ruminant, the ilium 
suilline. The femur and tarsus are much like those of the peccary. 
The known genera of this family are the following :— 
A. Orbit complete ; premolars four, the fourth with one ex- 
ternal crescent. First premolar below functioning as canine. 
a. No facial vacuities. 
Premaxillaries distinct; otic bullæ not inflated ; five digits 
in STU a a ee oa oo os ea oes Oreodon Leidy. 
Premaxillaries distinct; otic bulle inflated; four digits in 
manus......... hue ‘otaphus Leidy. 
Premaxillaries coössified ; otis RR inflated chess vied dances 
Merycocherus Leidy. 
aa. Facial vacuities present. 
Premaxillaries coössified, dentigerous; vacuities prelachry- 
mal OMY. eaeoe A a (is a Ca sccnn st Merychyus Leidy. 
Incisors six above, persistent; vacuities prelachrymal and 
prefrontal; nasal bones much reduced.....Leptauchenia Leidy. 
Incisors very few, caducous; vacuities as in Letanc phenia, 
very Intgë. aiiai siare aeaa e Bs Cyclopidius Cope. 
AA. Inferior premolars three. True inferior canine functional. 
Inferior incisors one on each side Pithecistes Cope. 
Starting from Oreodon as the ancestral form, Eucrotaphus follows 
at a little distance. The presence of the pollex observed by Scott 
in Oreodon proves that it must be referred to a five-toed common 
ancestor with Dorcatherium. The enlarged bullæ are added in 
Eucrotaphus, and the codssified premaxillaries in Merycochcerus 
and Merychyus. The latter commences the facial vacuities, which _ 
reach such huge proportions in Leptauchenia and Cyclopidius. 
The loss of the incisor teeth from both jaws, and diminished size, 
indicate that decadence is going on in Cyclopidius, but the last term 
is reached in Pithecistes. Here not only incisors but a premolar 
disappears. This family, once powerful in numbers, size and 
strength, disappeared with the Upper Miocene period in North 
erica, These relations may be thus displayed. A common 
ancestor with Dorcatherium is assumed. This will be a genus like 
Protoreodon S. and O., but without the caniniform inferior p. m. i of 
