562 ARCH ZOTHERIUM OF NEBRASKA. 
the upper maxilla, situated three-quarters of an inch above the crown of the second 
temporary molar, and two and three-quarter inches in advance of the orbit. 
The facial portion of the lachrymal bone is an oblong, quadrilateral plate, inclining 
forwards and upwards, and measures nearly two inches antero-posteriorly. 
Upper view.—The cranium proper viewed from above has a very striking resem- 
blance to thatof the Cats. The brain-cavity is much shorter, and is relatively nar- 
rower, and more uniform in its breadth. The summit of the sagittal crest and of 
the protuberance of the apex of the inion are broken in the specimen, but sufficient 
remains to obtain a good idea of the form of both. 
The apex of the occiput appears to have been quite as prominent as in the Tiger, 
though not so concave laterally, and posteriorly it appears to have been notched as 
in the Peccary. From it passes forward a high pyramidal sagittal crest, which has 
been about three inches in length to its bifurcation, which takes place just before 
reaching the coronal suture. The two branches proceeding from the crest are 
remarkably prominent and thick at their commencement, but gradually decrease in 
these respects, and diverge upon the frontal bone to the post-orbital arches. 
The forehead in advance of the bifurcation of the sagittal crest, and along its 
middle line, is deeply depressed and uneven. From one orbit to the other exclusive 
of its middle depressed portion it is convex. Anteriorly, in the specimens, the con- 
nexions of the frontal bone are broken away, but the other specimens described 
indicate the existence of angular processes, proceeding forward between the broad 
lachrymal plate and the nasal bones to join the upper maxillary, as in Choeropsis. 
Inferior maxilla.—Both fragments of the lower jaw are too much crushed to gain 
many characters of importance from them. That of the right side, which is best pre- 
served, is not quite two inches in depth below the first permanent true molar. Below 
the position anteriorly of the unprotruded last permanent premolar, a process pro- 
jects from the base outwards and downwards, like in Anthracotherium. 
Dentition—The superior anterior two permanent molars have been already 
described, and it is therefore unnecessary to say anything more about them in the 
specimen under examination, except that they are in a trifling degree longer, and 
the second is a little more convex at its sides; variations probably of a sexual 
character, but not improbably also only individual. 
The last upper true molar is smaller than those in advance, and is more convex 
at its sides. The basal ridge anteriorly, and first row of mammillary eminences 
are as well developed as in the preceding molars, but the posterior row has 
dwindled down in connexion with the corresponding portion of basal ridge into 
about four low tubercles. 
The superior two premolars described in one of the specimens, were so much 
worn that another description of the two preserved in the present one (Tab. x., 
fig. 1), which had not yet protruded, will be important. 
The crown of the last premolar is constituted by two large conoidal lobes, of 
which the internal is about one-third smaller than that situated external. At the 
base of the lobes, anteriorly and posteriorly, there exists a basal ridge ; better deve- 
loped and tuberculate in the latter position. 
