CENozoic (intebior). 293 
of Salmonidse, Catostomidae and Cyprinid£e. Absent: Elephas 
primigenius, etc. 
The Mammalian fauna of this epoch is little known, owing to 
the rarity of remains. Its characters may be chiefly learned 
from the numerous fresh- water fishes it contains, by which it may 
be compared with the Equusbeds, which also contain many fish 
remains. But one area of this epoch is known. It covers the 
southern part of Western Idaho, entering Eastern Oregon. 
TnucKEE. — The typical locality of this formation is the Kaw- 
soh Mountains in Western Nevada. The formation was supposed 
by King to be identical with the Johnday Miocene, but Dr. C. A. 
White informs me that it is of much later age. Vertebrate re- 
mains have been found, but have not been fully determined. 
Thickness (King), two thousand three hundred feet. 
Equusbeds. — Present : Glyptodontidse (Mexico), Megathe- 
riidse, Eschatiidse; extinct genera, Holomeniscus, Mastodon 
(Mexico), Smilodon (Texas); extinct species, JElephas primi- 
genius; Equus, four species; Lutra, Cervus, etc.; recent species 
of Thomomys, Arvicola, Castor, Canis, ? Homo. Absent : Coso- 
ryx, Oreodontidae, Protolabididaj ; Raiidse, Cobitidse, Mylocypri- 
nus, and the fishes of the Idaho beds in general ; Castoroides and 
Amblyrhiza. 
The localities of this formation are widely distributed. In 
the presence of various extinct forms, above mentioned, it agrees 
with the Pampean fauna of South America, but differs in the 
presence of the northern existing genera and species with the 
.extinct Elephas primigenius. The Argentine forms drop oif suc- 
cessively as we travel northwards. Thus, Macrauchenia ceases in 
Bolivia (Huxley), Toxodon in Nicaragua (Leidy), Glyptodon in 
the valley of Mexico (Barcena), where Elephas primigenius com- 
mences. Where the line should be drawn between the Pampean 
and Equusbeds I do not know, but we can arbitrarily assume it 
to be the line of distribution of the Elephas primigenius. This 
will include the fauna of the valley of Mexico, which has also 
other forms common to the more northern area. Such are four 
species of Equus, — one of Bos, one of Eschatius, one of Holo- 
meniscus (Camelidae), and one of Platygonus. 
The areas of the Equusbeds are, then, the valley of Mexico, 
Southwest Texas, Carson, Nevada, near Fresno, Southern 
