Cope.) 504. (Jan, 18, 
more inwards than the others, which it is supposed supported a nata- 
tory web. In the Oreodontide all the feet are regularly tetradactyle.* 
The Anoplotheriidx differ also in the presence of an additional cusp on. 
the inner side of the superior molars, accompanied by an imperfect de- 
velopment of one or both pairs of the internal crescents. In Anoplo- 
therium the internal crescents of the inferior molars are incomplete, and 
more or less represented by tubercles. In the Oreodontide there are two 
pairs of fully developed crescents, and no internal tubercles. The de- 
tails of the structure express various affinities. The axis is intermediate 
between that of the suilline and ruminant Artiodactyla; the other cer- 
vicals are suilline, while the remaining vertebre are ruminant. The 
scapula is ruminant, not suilline; while the humerus is like nothing but 
Anoplotherium. The radiocarpal articulation is intermediate between that 
of hogs and ruminants. The unciform supports the lunar bone. The sac- 
rum is ruminant, the ilium suilline. The femur and tarsus are much like 
those of the peccary. 
The genera of this family known to me are the following : 
I. Orbit incomplete ; last premolars in both jaws with two external 
crescents or Vs. 
PreniOlare THTOO! is eee Viele es eins vate wie eld th vivels ee mae COLOTCOQOTds 
PPHOMIOLATS TOUT) sie oasis oe ewige oop siumlecn iene ules Reha wiaontis Agriochoerus. 
IL. Orbit complete ; premolars four, the fourth with one external crescent. 
au. No facial vacuities. 
Premaxillaries distinct ; otic bullw not inflated. ..:....... vee ben Oneodon. 
Premaxillaries distinct ; otic bulle inflated. ................Mucrotaphus. 
Premaxillaries codssified ; otic bulle inflated. ......... ...- Meryeochoerus. 
aa. Facial vacuities present. 
Premaxillaries coéssified, dentigerous ; vacuities prelachrymal 
Wl disse eWeek Sesebes iin nlenyonyie. 
foal aN ai Oe I sete eee vee Mae ‘ 
Incisors six above, persistent ; vacuities prelachrymal and pre- 
frontal; nasal bones much reduced..... seeeeecececcee Leptauchenta. 
Incisors very few, caducous ; vacuities very large.........+.. Cyclopidius. 
Ill. Inferior premolars three. 
True inferior canine functional; inferior incisors one on each side. Pithecistes. 
The number of species referred to these genera in the succeeding pages 
is as follows : 
Oreodon. wines CVG Ueno 
Eucrotaphus. Pe Svate a's MIR UNK DEER ik é 
Merycocheerus. «1... seer eee cues Fv cisco be dca legumes shiner ye 
Merychyus........ See IR REVI Ch Hel Chose Uie Sele Wigals Mia RACAL A os) 
Leptuuchenia...... .....- SEL aRnE LSE AO Vee sal aeee é 
Oyclopidiuis........ cece eee cece ieee ees 2 
Pithectetesy ss. oes eevee seule Pit ecain's atacwey é 
Agriochoerus . sen 6 
Coloreodon... 2 
35 
* I have observed this in the genera Oreodon, Eycrotaphus, Merycochorus, 
and Merychyus, 
