POEBROTHERIUM. 21 
The only parts preserved and visible of the base of the cranium, in the speci- 
men, are the auditory bulla, separated by the body of the sphenoid bone. These 
are remarkable for their great size and position. Relatively they are not longer 
than in the Musks, but their transverse and antero-posterior diameters are rather 
greater. They are also more vertical in their position than in the Musks, and 
are so situated that their postero-external portion projects considerably exterior 
to the ramus of the lower jaw, fillimg up nearly a concavity formed by its posterior 
margin. The length of the bulle from the meatus auditorius is eleven lines, the 
transverse diameter posteriorly nine lines, and the antero-posterior diameter an 
inch. Externally they are convex, and converge forwards within the position of 
the ramus of the lower jaw; internally they are vertical and slightly convex, or 
nearly plane; posteriorly they inclose the stylal pit; and postero-internally they 
present a broad irregular surface, which abuts against the paramastoid process. 
The space separating the bulla, or the width of the sphenoidal body between them, 
is about five lines. (Fig. 1.) 
The auditory process resembles that of the Musks, and the meatus auditorius 
externus, which holds the same relative position as in these, is subcircular, and 
about a line in diameter. 
The glenoid articulation, so far as can be ascertained by viewing its position with 
the condyle of the lower jaw in contact, is much like that of the Musks, but 
appears rather more concave. 
Inferior Maxilla—The form of the lower jaw in Dorcatherium is very similar 
to that of the recent Musks, but is very peculiar in Poebrotherium. In this the 
base is much more nearly horizontal, and when placed upon a plane surface touches 
it at the angle and middle, and the anterior portion, which curves downwards from 
the position of the third premolar to the symphysis, also nearly reaches the same 
level. (Fig. 1.) 
The outer surface of the bone below the true molars is convex, but below the 
premolars is nearly plane and deeper than in the former position. The alveolar 
margin rapidly ascends posteriorly from the position of the second true molar, and 
descends in advance of the second premolar. 
The ramus is remarkable for its breadth, and the possession of an angular 
apophysis, as in the Camel, carnivora, and most rodentia. The process in position 
and form is intermediate to that of the Camel and Rabbit. From its point a thin 
conyex edge, corresponding to the technical angle, descends to the base of the jaw, 
and a concavity, which in a great measure is occupied by the auditory bulla, ascends 
to the condyle. 
The relation of the condyle and coronoid process is about the same as in the 
Musks, but below the notch separating them, the ramus is depressed relatively as 
much as in the Peccary, a peculiarity in which the genus differs from all existing 
ruminants. 
The condyle externally has nearly the same form as in the Musks, and as far as 
can be seen in the specimen; its articular surface appears to be a little more convex 
than in those animals. 
The coronoid process is relatively broad, and curves upwards as in the Musks. 
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