OREODON. 55 
Comparison between OREODUN CULBERTSONIL and OREODON GRACILIS. 
Besides the great disproportion in size between Oreodon Culbertsonii and Oreodon 
gracilis, (the latter being nearly one-third less than the former,) there are other 
differences which, though slight, are important. 
In Oreodon Culbertsonii, the sagittal crest rises from the sides of the temporal 
fossee in a gradual pyramidal manner; but in Oreodon gracilis, the intertemporal 
region at its upper part is more arched, and the sagittal crest rises from it in the 
form of a thick, abrupt, rugged, linear ridge. 
In the latter species the lachrymal depressions are relatively less deep, and the 
entrance of the orbits more nearly circular. 
The posterior convergent extremities of the ossa nasi terminate more abruptly 
in Oreodon gracilis ; or in this they are convex and in Oreodon Culbertsonti are 
angular. 
The ossa tympanica are relatively much more inflated in Oreodon gracilis; and 
the prominent ridge continuous from them to the auditory process in Oveodon 
Culbertsonii, is but feebly developed in the former species. 
. Oreodon major, Lery. 
(Pu. IV., Fig. 6.) 
Syn. Merycoidodon major. 
A third species of Oveodon with some hesitation is proposed upon a fragment of 
the right side of the upper jaw, containing the true molars, from the collection of 
Dr. Owen. 
The specimen belonged to a middle-aged individual, as indicated by the tritura- 
tion to which the teeth have been subjected in mastication; the characteristic 
enamelled grinding surface of the first true molar being quite obliterated. 
The teeth correspond closely in form with those of Oreodon Culbertsonii, but 
they are much larger than any of the specimens which have been attributed to the 
latter. 
It is not improbable, that upon further investigation, the specimen may prove 
to belong merely to a large variety of Oreodon Culbertsonii, for the difference in 
size of the teeth from those indicated in the specimen 10, of the latter species, is 
not as great as that existing between the teeth of this and those of specimen 16. 
MEASUREMENTS. 
Inches. Lines. 
Length of series of upper true molars . : 2 : : 2 33 
Antero-posterior diameter of the last molar . é : : : : a a! 
11 
Breadth anteriorly 
