EQUIVALENCY OF BEDS. 



41 



mostly to existing genera, the chief exception being Hippotherium. The 

 horses are chiefly represented by Equus. Common genera are Ardomys, 

 Lepns, Elephas, Mastodon, Tapirus, Sus, Cervus, Antilope, Bos, Canis, Drepa- 

 nodon, Felis, Ursus. In the Equus beds of Oregon a few extinct genera in 

 like manner share the field with various recent ones, while not a few of the 

 bones are not distinguishable from those of recent species. I give the fol- 

 lowing list, the extinct species being in italics : 



Mylodon sodalis. Canis latrans. 



Thomomys (nr.) clusius. Elephas primigenius. 



Equus occidentalis. 



Equus major. 



Auchenia hesterna. 



Auchenia magna. 

 Auchenia vitakeriana. 

 Cervus fortis. 



Thomomys talpoides. 



Castor fiber. 



l/utra near piscinaria. 



The species derived from the cave formations of the Eastern States 

 are more numerous, and diflfer from the Oregon fauna in many respects ; 

 yet the parallelism is close in the genera with the Equus beds on the one 

 hand and the Pliocene of Europe and South America on the other. The 

 differences distinguishing it from the Equus beds of Oregon are, however, 

 such as compel me to regard it as a distinct division of the Pliocene, under 

 the name of the Megalonyx beds.* 



Megatherium (p). 

 Mylodon (p). 

 Megalonyx (p). 

 Sciurus (s). 

 Arctomys (s). 

 Jaculus (s). 

 Arvicola (s). 

 Erethizon. 

 Hydrochcsnis (p). 



Castoroides. 

 Lagomys (s). 

 Lepus (s). 

 Anomodon. 

 Scalops. 



Arctotherium (p). 

 Procyon. 

 Canis (sp). 



DrepanodonSmilodon (vel). 

 Mastodon (sp). 

 Equus (sp). 

 ? Hippotherium (s). 

 Tapirus (s). 

 Dicotyles (p), 

 Cariacus (p). 

 Bos (s). 



Mustela (sp). 



In the above list the extinct genera are marked in italics. There 

 exists, as a marked feature of the North American Pliocene, to which I called 

 attention several years ago,t a considerable representation of the fauna of 



*BuU. U. S. GeoL Surv. Terrs, v, p. 5a, 1879. 



\ ProcAoad. PhUa. 1857, 156; Proc. Am. Philos. Soc. 1869, 178. 



