1887] Mesozoic and Cenozoic of North America. EOT 
include the fauna of the valley of Mexico, which has also other 
forms common to the more northern areas. Such are four species 
of Equus, —one of Bos, one of Eschatius, one of Holomeniscus 
(Camelidæ), and one of Platygonus. 
The areas of the Equus beds are, then, the valley of Mexico,” 
Southwest Texas, Carson, Nevada,’ near Fresno, Southern 
California, the Oregon Desert, Western Nebraska,:and prob- 
ably other localities. The beds are nowhere of great depth. 
The presence of Homo in the beds of this epoch in Oregon 
was indicated by me in 1878.77 This discovery has been con- 
firmed by the discovery of obsidian implements in place, in 
Western Nevada, as affirmed in a recent publication” of Mr. G. 
K. Gilbert of the United States Geological Survey in Nature. 
This gentleman has expressed the belief that the beds of this 
age are not older than the glacial epoch, because they embrace 
the bases of some of the moraines of some of the ancient glaciers 
of the Sierra Nevada. It remains to be proven, however, that 
these moraines are of true glacial age, since they are of entirely 
local character. The presence of so many mammals of the fauna 
of the valley of Mexico would not support the belief in a cold 
climate. 
Tue Mecaonyx Bens. —This formation is chiefly represented 
in the caves of the Eastern States. Its fauna is as follows: Present: 
Megatherium, Mylodon, Megalonyx, Castoroides, Amblyrhiza, 
Anomodon, Arctotherium, Smilodon, Platygonus, Mastodon, of 
extinct genera ; and of recent genera, Sciurus, Arctomys, Jaculus, 
Arvicola, Erethizon, Hydrochcerus, Lagomys, Lepus, Scalops, 
‘Procyon, Canis, Mustela, Equus, Tapirus, Dicotyles, Cariacus, 
Bos, Didelphys. Absent: Glyptodontide, Eguus crentdens, occi- 
dentalis, and ġarcenæi; Eschatiide, Holomeniscus. 
It is not certain that this fauna does not owe its peculiarities 
to geographical causes only, and was not entirely cotemporane- 
ous with the epoch of the Equus beds. Its relations to that of 
the glacial epoch are not yet fully defined. 
PLISTOCENE SYSTEM, 
; . e . Ap re 
This system is represented by but few deposits in the interior 
of North America. Therefore it is touched on but lightly in 
this report. The consecutive epochs which it embraces are the 
following : 
