72 ON THE EXTINCT MAMMALIA OF 



What are supi^osed to be the bones of the fore ami and leg are discrete, as in the 

 Hog, and the bones of the feet correspond in number with those of this animal. 



The species l^elonging to this family I have referred to"^ four genera, Avhich are 

 closely allied, and indeed are not separated by any very striking characters. Perhaps 

 most naturalists would include them in a single genus, nor am I prepared to dispute 

 such a view. 



The genera are named Oreodon, Merycochoerus, Merychyus, and Leptauclienia. 



The first genus, Oreodon, includes three species, besides scAcral doubtful ones, or 

 well-marked varieties. Their remains are by far the most abundant of those which 

 have been brought from the Mauvaises Terres of White Elver. Occurring most fre- 

 quently in bed B of Dr. Havden's section of the miocene formation, they also extend 

 into the higher beds C and D of the same section. Oreodon Gulhertsoni and 0. gra- 

 cilis especially belong to the lower bed B, Init 0. major appears to have been a 

 rather later form, and belongs to the higher bed D. 



Merycoclicerus belongs to the latter bed, and looks as if it might have been a 

 derivative of its cotemporary 0. major. 



Merychyus is represented by three sj^ecies, the remains of which were obtained from 

 bed F of Dr. Hayden's section of the pliocene formation of the Niobrara River. 

 These look as if they might have been derived, perhaps by selection, according to the 

 view of Darwin, from one or other of the species of Oreodon of the preceding period, 

 from Merycoclicerus, or from the succeedmg genus. 



Leptauchenia is represented by three species, the remains of which pertain to l^ed 

 D of Dr. Hayden's section. 



OREODON. 



Of the great variety and aljundance of mammalian fossils brought from tlie 

 Mauvaises Terres of White River, by far the most numerous belong to a remarkable 

 and peculiar genus of ruminants, which we have distinguished by the name of 

 Oreodon. In the various collections of fossils from the locaUty mentioned which have 

 been submitted to my inspection, I have estimated that I have observed skulls, frag- 

 ments of others and teeth, together with other bones of the skeleton, of perhaps five 

 hundred individuals of Oreodon, referable to three distinct species. With compara- 

 ti\'oly few exceptions, the specimens belonged to a species of intermediate size, to 

 Avhich I have given the name of Oreodon Culberisoni. Those of the largest species, 

 Oreodon major, are rare, comprising not more than one or two per centum of the 

 whole. Specimens of the smallest species, Oreodon gracilis, are more abundant, — 

 equal to about ten per centum of the whole. 



Oreodon, m tlie anatomical character of its skeleton, exhilnts a clear relationship to 

 sudlnie animals, and, indeed, tlie character of the genus cannot probably be better 



