49 OREODON. 
= 
internally the last premolar is excavated into a quadrilateral cul-de-sac, of which 
the inner boundary is a pyramidal tubercle, the homologue of the postero-internal 
lobe of a true molar. The outer apex of the tooth continues inward upon the sum- 
mit of a pyramidal sub-lobe, apparently homologous with the antero-internal lobe of 
a true molar. In advance of this sub-lobe, there is a broad notch sloping to the 
base of the tooth. 
The second premolar exhibits internally a rudimentary form of the correspond- 
ing portion of the tooth behind. The tubercle has disappeared; and the sub-lobe 
in advance of this has degenerated into an oblique ridge descending obliquely 
backward from the summit of the tooth. The surface postero-internal to this ridge 
is sloping, and receives from it a slight abrupt offset. Anterior to the ridge, the 
internal surface presents a simple, broad, sloping depression. 
The first premolar exhibits internally a simple ridge descending from the summit 
obliquely backward, and dividing the surface into two depressions, of which the 
anterior is the broader. 
In tracing upon the premolars, among our specimens, the effects of mastication, 
it is observed that when the enamel is nearly obliterated from the triturating sur- 
faces of the true molars, the bottom of the posterior cul-de-sac in the third premolar 
is left as a small oval islet of enamel upon a broad shoe-formed surface of dentine ; 
while the second premolar is worn so as to present a surface of dentine having the 
form of a Greek ¢. (VI. 8.) 
As in existing ruminants, the inferior molar teeth of Ovreodon are inserted by 
two fangs placed one before the other. The last molar having a fifth lobe, the pos- 
terior fang is proportionably broad, and is constituted by a confluent pair. 
Canines.—(P1. Il. Figs. 1, 3; II. 1, 2.) The possession of well developed 
canine teeth in both jaws, is one of the most remarkable characteristics of Oreodon. 
The form of these teeth is peculiar; neither those above nor below grow from per- 
sistent pulps; and only the crowns are capped with enamel. Those which I have 
concluded to belong to the male of Oveodon, are more robust than those attributed 
to the female. 
The upper canine, commencing at the extremity of its fang above the interval 
of the first two premolars, curves forward, downward, and in a less degree outward. 
In the male, it is directed more externally than in the female. The fang of the 
upper canine renders the face slightly prominent along its course, and is trihedral, 
with rounded margins, and approaches more or less a cylindroid form. In some 
specimens it is flattened, or nearly so, upon the outer side, and exhibits one or two 
slight flutings at the lower part. 
The crown is a trihedral pyramid, with the lateral margins acute, the anterior 
margin subacute, and the summit pointed. Its sides are nearly equal; one being 
directed outwardly, another inwardly and forward, and the third posteriorly. The 
first is nearly plane; and the second is also nearly plane, and presents a median 
obtuse ridge, which vanishes above in the fang, and below towards the point of the 
crown. The remaining side is visible in only one specimen; its enamel is worn 
off, excepting a small portion at each basal angle; and it is quite plane and smooth, 
and is a little larger than the other sides. 
ee 
