LOUP FOEK EPOCH. 
363 
Eodentia. 
White River. 
Anchitherium. 
Hyracodon. 
Aceratherium. 
Menodus. 
Symborodon. 
Palseolag’us. 
Eumys. 
Heliseomys. 
Gymnoptychus. 
Iscbyromys. 
Loup Fork. 
Aphelops. 
Panolax, 
?Eumys. 
Steneofiber, 
Dr. Leidy, in liis work on the Extinct Mammalian Fauna of Dakota 
and Nebraska, enumerates several genera of the existing fauna as having 
been discovered by Dr. Hayden in the Loup Fork beds. Such are Hystrix, 
Castor, Equus, and Bicotyles, Many of the specimens referred to this epoch 
are stated to have been derived from the sands found along the banks of 
the Loup Fork, which are composed of sediments of a mixed character, some 
of the specimens being, in Dr. Leidy’s opinion, of Quaternary age, and 
others, especially some referred to Cams and Eqims, belonging to existing 
species. I possess a specimen of a cranium of a Tliomomys from the sands 
of the Big Blue River, Kansas, wdiich, in like manner, I am unable to dis¬ 
tinguish from an existing species. These sands are probably the deposits 
of more than one epoch, being primarily derived from the bluffs and mesas 
of the true Loup Fork formation, carried to the lowest level, and inclosing 
remains of species of Quaternary and those of modern age. These reflec¬ 
tions are not due to my own examinations of the region in question, which I 
have not visited, but for the following reasons: 
The fossils of this epoch from Colorado and New Mexico which I 
have described were all found in place by myself, and excavated by my 
own hands or in my presence. The specimens are numerous, especially 
those from Colorado. I have not found the modern genera above men¬ 
tioned as enumerated by Dr. Leidy, nor any others of modern or Quater¬ 
nary character. On the contrary, the result has been to isolate the Loup 
Fork fauna from the Quaternary as well as from the White River epochs. It 
includes three existing genera of Mammalia only, one of which. Cams, 
