P^\L/1^0MAST0D0N. 
137 
interrupted opposite the front lobe of the last molars by a pair of elongated apertures, 
the posterior palatine foramina {p-P-f-)- The upper edge of the palatine seems to 
extend up into the side of the skull above the maxilla, where it joins the lower edge of 
the orhitosphenoid. 
'I'he vomer (text-fig. 49, v.), as already remarked, extends backwards considerably 
behind the level of the posterior border of the hard palate and forms a long V-shaped 
crest along the roof of the nasal canal. 
In this specimen the upper portion of the maxilla {mx.) is broken away in front, so 
that its relations in that direction cannot be determined. The alveolar region is very 
long and almost straight, there being only a very slight outward convexity ; it bears 
six cheek-teeth (three premolars and three molars). The base of the zygomatic 
process is long and nearly parallel with the alveolar border, from which it is separated 
by an interval of about 3 cm. : the anterior end is about opposite the front of m. 3. 
The upper surface is concave and forms the lower border and floor of the orbit. 
Anteriorly it is perforated by the antorbital foramen, which, judging from the young 
skull described below, had two openings on the face — a lower larger one preserved 
in the present specimen, and a smaller upper one here broken away. The much 
smaller size of the antorbital foramen in Palceomastodon compared with that seen in 
Elephas, is no doubt due to the fact that in the older form the proboscis was still 
comparatively small. 
Behind the orbit there is a small upwardly directed process of the zygoma, 
marking the anterior limit of the jugal, which sends forwards a long process 
overlapping the maxilla and helping to bound the orbit. The form of the suture 
between the jugal (ju.) and the maxilla [mx.) will be best understood by examination 
of the figure (PI. XII. fig. I). The palatine plates of the maxilla are rather narrow 
and together form a palate which is gently arched from side to side ; posteriorly they 
are separated by the palatines as above described. Behind the last molar the bone 
is greatly thickened by sinuses, so that, although the dentition is still of a perfectly 
normal type, the increase in the size of the hinder part of the maxilla, which is 
carried to such an enormous extent in the later forms, in which the teeth are 
greatly enlarged, has already begun to manifest itself. Superiorly the bone appears 
to unite with the orhitosphenoid in a straight suture running forwards and downwards. 
The anterior portion of the orbital region is wanting. The maxilla, as might be 
expected from the character of the dentition, differs widely from that seen in 
the Elephants. The chief differences are : (I) the much greater relative length 
of the bone ; (2) its smaller depth consequent upon the brachyodont character of 
the teeth. These features are especially noticeable posteriorly, where, except for the 
development of the sinuses in the bone behind m. 3, there is no trace of the enormous 
increase in size in all dimensions, but especially in depth, which has taken place in 
Elephas in consequence of the immense size of the posterior molars and their mode of 
