n_ 
62 ARCHAEOTHERIUM. 
the lachrymal bone, to about the middle of the position of the penultimate molar 
tooth. 
Inferior Maxilla.—Of the lower jaw we have the opportunity of examining only 
several small fragments, but fortunately these are important ones, as from the form 
of the superior molar teeth resembling very closely those of Choeropotamus, we 
might expect to find a lower jaw constructed like that of this animal, which is far 
from being the case. One of the fragments consists of the posterior extremity of 
the right side, externally attached to a mass of matrix. (X. 7.) The coronoid process 
and condyle are broken, but they appear to have preserved their relative proportion 
and position to one another, which are as in modern suilline animals. The tech- 
nical angle, which is preserved entire, is not prolonged into a hook as in Choeropo- 
tamus, nor is it rounded as in the Hog and Peccary, but is almost rectangular, and 
lengthened slightly backward and downward, as in the Deer; and it is thick and 
convex at the apex. The ascending ramus is broad, and, as in the Hog, is apparently 
not depressed to any extent in advance of the position of the condyle. The pos- 
terior border of the jaw is vertically concave; gnd, indeed, excepting the condyle 
and coronoid process, the posterior part of the bone partakes of the form of that of 
the Hog and Deer. 
The other fragments are portions of the lower jaw of both sides containing molar 
teeth; and are two inches in depth below the position of the first true molar. That 
of the right side is an exceedingly interesting and important piece (VIII. 2), for, as in 
Anthracotherium, it has a short obtuse process projecting from the base of the bone. 
The direction of the process is outward and downward, and it is situated below the 
position anteriorly of the last permanent premolar. From the outward curve of 
the process the jaw above and on a line with it is concave. 
Dentition—Of the permanent dentition of Archacotherium we are acquainted 
only with the posterior five upper molars, and the posterior four below. These are 
constructed upon an undoubted suilline type, but approach none of the recent forms 
so much as they do those of Hyracotheriwm, or more those of Choeropotamus, and 
most, if they are not identical with, those of Hntelodon. 
In the specimens, the molar teeth above mentioned form a close row in both 
jaws, and their relation to one another is the same as in the Hog, Peccary, or 
Hippopotamus. 
Superior Molars.—(VIII. 2; [X.1, 3-5; X.1.) The upper true molars are con- 
structed after the same type as rie of Choeropotamus and Hyracotherium, but differ 
principally in the less extent of development of the basal ridge. 
The crowns of the anterior pair of true molars are quadrate with convex sides, 
and internally as in Entelodon magnum have no basal ridge like that existing in the 
other two genera mentioned. The grinding surface of these teeth presents two 
transverse rows, each of three conical lobes, of which those external and that 
antero-internal are the larger, and are nearly equal in size; and the remainder are 
subequal. 
The enamelled sides of the lobes are corrugated and their apices are excavated, 
though feebly, compared with what they are in Hyracotherium and Choeropotamus. 
