540 OREODON OF NEBRASKA. 
with mineral matter, indicate that they have been submitted to great pressure or 
violence, while embedded in the deposit in which they are found when this was in 
a soft state, or in the condition of mud. 
The specimens are very dense, and in many of them the Haversian canaliculi 
and areole, and in the case of the long bones the medullary cavities, are filled 
partially or completely with silex. In the latter positions, the silex is sometimes 
beautifully crystallized, or has a botryoidal, chalcedonic arrangement. 
The change which has taken place in the chemical constitution of these fossilized 
bones has been determined through analysis by Dr. Owen, and is given in his 
report. 
OREODON. = Leidy. 
(Tab. x., 4-6; xi. 2, 3; xiii., 3-6.) 
In Volume IV., page 47, of the Proceedings of the Academy of Natural Sciences of 
Philadelphia, I described a fragment of an upper and lower jaw, from the Bad 
Lands of Nebraska Territory, presented to the Academy by Mr. Joseph Culbertson. 
The former fragment contained the two posterior molars, the latter the three posterior 
molars, and upon them was characterized the new genus and species Merycoidodon 
Culbertsonii. In 1851, I received from Professor Baird of the Smithsonian Institu- 
tion, and Dr. Hiram A. Prout of St. Louis, several fragments of skulls and jaws 
from Nebraska Territory, having the same form of true molar teeth characteristic 
of Merycoidodon; but being misled by a fragment of a face of a young animal con- 
taining a portion of the first permanent premolar, followed by the entire first, and 
a portion of the second deciduous premolars, and portions of the deciduous true 
molar, and first permanent true molar, in a verbal communication to the Academy,* 
I stated that the specimens belonged to two other distinct genera, to one of which the 
name Oreodon was applied, of which two species were designated: O. priscum, and 
O. gracile ; to the other, that of Cotylops, distinguishing the species as C. speciosa. 
All these have since been satisfactorily determined to belong to two species of one 
genus, for which I propose to retain the name Oreodon, as being less exceptionable 
than that of Merycoidodon ; for it will be observed, from the anatomical details pre- 
sented in the succeeding pages, that the animal was a true Ruminant, and did not 
merely resemble one in the form of its true molar teeth.+ 
e abundance of remains of Oreodon found associated with those of Palwothe- 
rium, Rhinoceros, Machairodus, ete., in the Eocene formations of Nebraska, lead to 
the impression that it completely replaces the Anoplotherium of Europe. We have 
in possession, and belonging to the collections of the Smithsonian Institution, Dr. 
D. D. Owen of New Harmony, Indiana, and Dr. Hiram A. Prout of St. Louis, Mis- 
* Proc. A. N. S., vol. v. p. 237. 
7 After detecting the error just related, it was some consolation to me to find that even some of the 
most distinguished of modern anatomists have been misled under exactly similar circumstances, to the 
special cases of which I think it needless to refer. 
