ARCHAEOTHERIUM. 59 
root, and from this position it turns directly forward and terminates by resting 
upon a long rectangular notch of the malar bone. 
The posterior half of the outer surface of the zygoma forms a nearly vertical 
plane; but anteriorly, where formed by the malar bone, it is remarkable for its 
extraordinary depth; being over two inches, and is vertically plane above, but 
slightly bent outwardly below. 
In the specimen, the sagittal crest is broken at the inion and along its free mar- 
gin, but it is yet sufficiently entire to exhibit the remarkable uniformity of its . 
height in comparison with that of the Camel and Lion. Posteriorly, as in the 
two latter, it has the appearance of having contributed to the formation of a strong 
process overhanging the inion, but it is not as concave laterally as in either of 
these animals. 
The margin of the temporal fossa bordering upon the inion is acute, but forms 
no trace of a projecting crest. 
The post-orbital process of the os frontis is as thick and strong as in the Camel; 
and, as in this, has nearly the same direction outward and backward, and it joins 
an equally short and strong process of the os male. 
The temporal surface along the sagittal crest is concave, but below the base of- 
this is uniformly convex in the vertical direction. 
The orbit is relatively larger than in the Hog or Peccary, and is broader below ; 
is vertical and ovoidal at its entrance, and is directed outward and forward at an 
angle of about 45°. Its superior margin is prominent and obtuse, and the lachry- 
mal border forms a simple, compressed mammillary eminence, bounded above and 
below by a rounded notch. Just internal to the lower notch is a single lachrymal 
foramen. Below the orbit the malar bone is remarkably shallow, and its surface, 
from the infra-orbital margin, slopes outward, downward, and backward. | 
The post-orbital arch is even relatively stronger than in the Camel, and has 
about the same form. The possession of this arch by Archaeotherium is a remarka- 
ble peculiarity, as it does not exist in the closely allied Choeropotamus, nor in any 
of the recent suilline genera, except as an inconstant characteristic in the Hippo- 
potamus. 
The side of the face is vertically convex, and is directed forward in a straight 
line from the position of the termination of the malar bone. 
The outer face of the lachrymal bone is slightly bent and nearly plane and ver- 
tical. The infra-orbitar foramen is vertically oval, and is situated above the posi- 
tion of the penultimate premolar, and nearly three inches in advance of the orbit. 
Superior View.—(Pl. 1X. Fig. 2.) In the upper view of the head of Archaeo- 
therium, the cylindrical form of the interparietal region, bounded above by the 
high sagittal crest, is a striking peculiarity of the genus. 
Between the zygomata the breadth of the head is relatively greater than in feline 
animals. 
The space inclosed by the zygomatic arches is as capacious as in the Lion, but 
is relatively a little longer and not quite so broad, and is oval in form. 
The forehead and prognathous face much resemble those of the Hyracotheriwm. 
