This species was considerably larger than _Palæosyops major_, with
which it shows affinities, as also with _Titanotherium Proutii_. See
Plate IV.
The _Frontal_ is narrow and flat, or slightly arched. It sends out a
strong curved postorbital process, which projects outwards, but not
so much outwards as in _Palæosyops_. The sagittal crest runs back
from the postorbital in a low rounded ridge, rising but little as
it recedes. The superciliary ridge is distinct, and is pierced by
two small venous foramina. The shape of the entire bone is much as
we find it in the dog, except that it does not arch so much. One of
the most marked differences between this genus and _Palæosyops_ is
here shown. In the latter the forehead rises abruptly from behind
the orbit, while in the former there is only a slight rise for
some distance behind the orbit. As the bone is broken here, it is
impossible to state whether there is any rise at all. Probably not,
however. Below the postorbital process, on the lateral aspect of
the bone, there is a low ridge which separates the orbit from the
temporal fossa. The under surface of the frontal is smooth.
The _Nasal_, of which but a small portion is preserved, is flat on
top, but bends downward at the angle.
The _Maxillary_ is long and stout, over the last and penultimate
molars it broadens to form the floor of the orbit, which is of
unusual size. Between the canine and the malar the maxillary arches
inwards, forming a perceptible concavity, at this point it reaches
its greatest vertical height, as it rises to join the nasal. The
alveolar border is curved in two directions, one with the convexity
outwards, and the other downwards. It exhibits no emargination in the
diastema between the canines and molars. The palatine plate is long,
thick, and narrow; it is flat fore-and-aft, but concave transversely,
owing to the elevation of the alveolus; the suture also is raised
slightly. In thickness it varies; being thickest between the canine
and the second premolar, and beyond this becoming thinner. Its
forward termination seems to be obtuse, running for a short distance
along the premaxillaries. The infraorbital foramen is large, situated
over the fourth premolar, lower down, and nearer to the malar than in
_Palæosyops_.
The _Premaxillary_ is rather short and stout; it is slightly
compressed, and ends in a sharp keel on top. Although not so thick
as in _Palæosyops_, it is much larger vertically. The inner surface
is ridged; it has no palatine process, and no spine, so that the
incisive foramen is large and undivided. There was no symphysis
between the two premaxillaries, they do not show even any articular
faces for each other, so that they may not have been in contact
during life. The animal was adult, but not old. The incisive alveolus
is short and straight, and is but little out of the line of the
molars. There is a very long diastema between the incisors and the
canine, and here the premaxillary is deeply notched to allow the
passage of the lower canine.
The _Malar_ is very different in shape and size from the same bone in
_Palæosyops_. Its facial extent is greater, as it articulates with
the maxillary as far forward as the first molar. It is not so broad
from above downwards, but is considerably thicker; the articulation
with the squamosal is by flat surfaces. The postorbital process is
small and indistinct. The orbit is of great size; its breadth, shown
by the maxillary floor is unusual, but its fore-and-aft diameter is
extreme, being nearly twice as great as in a large _Palæosyops major_.
The _Squamosal_ is a short, slender, and trihedral bone; it is not
at all like the squamosal of _Palæosyops_. It is smaller even than
that of _P. paludosus_; its outer margin is not turned up, making the
upper surface concave; it does not project much outward, and scarcely
at all downwards, as this is rendered unnecessary by the flatness of
the forehead. The chief difference, in the size of this bone, between
this genus and _Palæosyops_ is found in the much greater vertical and
lateral diameter of the latter; in length they are about equal. The
glenoid cavity is large, shallow, and transverse.
As a whole, the zygomatic arch is comparatively slender; it is
rounded, and does not project much laterally from the side of the
head; but its chief peculiarity consists in the fact that it is
nearly horizontal. It is thus altogether different from the arch of
_Palæosyops_.
The _Occipital Condyles_ are different from those of that genus.
They are flatter, shorter from above downwards, and proportionately
much smaller; but are expanded laterally in much the same manner. At
the border of the foramen magnum they are gently rounded instead of
having a sharp angle. These borders are segments of circles, but as
the condyles are broken from the rest of the occiput, we cannot infer
from this the shape of the foramen.
The _Mandible_ is long, stout, but comparatively shallow. It is
of nearly uniform thickness throughout, and does not exhibit the
thickening of the alveolus and thinning, of the lower margin, which
is shown in _Palæosyops_, especially in _P. major_; and the downward
and inward arching of the alveolar border is not marked to the same
extent as in that species. The lower border is nearly straight,
and has but one slight emargination just behind the symphysis. The
ascending portion of the ramus rises near the last molar quite
abruptly, and makes an angle of nearly 90° with the horizontal
portion. The masseteric fossa is shallow and obscure, and the
anterior bounding ridge is almost obsolete. This part of the jaw is
very different from any of the species of _Palæosyops_. The symphysis
is quite long, and extends back as far as the second premolar; the
chin is probably rounded. The dental foramen is situated high up in
the ascending portion of the ramus; the mental foramen is placed
below the second premolar; it is large and single.
_Cranial Measurements._
M.
Breadth of frontal at postorbital process ·045
Breadth of frontal in front of postorbital ·030
Breadth of nasal just in front of orbit ·032
Length from angle of nares to end of premaxillary ·1235
Length of premaxillary ·056
Length of maxillary ·230
Breadth of palatine process at canine ·026
Breadth of palatine process at second premolar ·029
Vertical height of maxillary at angle of nares ·064
Breadth of maxillary across floor of orbit ·058
Fore-and-aft diameter of orbit ·054
Length of malar along maxillary ·094
Vertical diameter of malar behind maxillary ·029
Transverse diameter of malar behind maxillary ·033
Fore-and-aft diameter of glenoid cavity (about) ·029
Vertical diameter of squamosal at end of malar
articulation ·032
Transverse diameter of squamosal at end of malar
articulation ·0325
Length of ramus mandibuli from symphysis to
ascending portion ·177
Depth of jaw at last molar ·068
Depth of jaw at second premolar ·061