DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 253 
The under view (Plate 37, fig. 1) is remarkable for its size, both in length and breadth ; 
its length is considerably greater than that part of the basis cranii which lies behind 
it, and its breadth is equal to that part—the main part—which is formed by the 
maxillaries and palatines. The general form of the palatine region is oval, but 
irregular in front, and emarginate behind. Laterally the large alveolar tracts with 
their pushing teeth (some of them are cut) are very large ; there are no teeth in the fore 
part of the premaxillaries, but two in each, on the side; these, however, are small. 
The fore margin of the premaxillaries is narrow, where they meet in a very obtuse 
angle; the lateral part of each bone projects forwards, and is subuncinate. The 
slender palatine processes of the premaxillaries (p.px.) are hidden, behind, by the 
maxillary palatine plates ; when these are removed (Plate 39, fig. 1) then they can be 
seen as long, slender, arcuate, compressed bars, having no distinct antero-lateral 
vomers attached to them; but these bones may have become confluent with them. 
Through the narrowness of the premaxillaries in front, and the deficiency of the 
maxillary plates towards the mid-line, the anterior palatine foramina are very large ; 
they are oval, and show a considerable tract of the recurrent cartilages (7¢c.c.), behind 
the opening of JAcoBson’s organs (/j.0.). Behind the emargination the maxillaries 
scarcely meet for some distance, but the last two-thirds of their suture is perfect ; 
right and left of this part the bone is concave, but this hollowing of the roof is much 
less than that which is found in young Marsupials; the sides also are hollow, thus 
there is a general crescentic convexity along the middle of each palatine plate. The 
hard palate is not extended backwards more than one-sixth further by the palatines 
(pa.), but they are strong bones, and the whole hard palate shows nothing of that 
economy of bony deposit seen in Marsupials and typical Insectivores. The skull set 
up, and with the palate towards the eye, shows, here, a very elegant double archway 
to the two nasal passages. The thick, ribbed margin of the bones projects where they 
meet, so that the end of the hard palate is bracket-shaped ; in front of each thickening 
the oblique posterior palatine foramen (p.p.f.) 1s seen. These narrow curved 
palatines lie like scales under the maxillary plates, and their curved thin fore edge 
retreats, laterally, and then turns a little inwards, where it is pressed against the 
alveolar wall of the two last teeth. The thick side wall of the open part still gently 
curves inwards ; it is separated outside from the palatine portion by a large sharp 
notch. The shell-like orbital or ascending part of the palatines meets the hinder part 
of the main vomer (v.), almost reaching as far backwards as its four terminal prongs. 
The small pterygoids ( pg.) also ascend, and below, where they are spliced obliquely to 
the palatine wall of the great nasopalatine canal, they end, behind, in the hamular 
process, which is small, flat, and turned outwards; it is supported, outside, by 
the equally small external pterygoid process (e.pg.). The pterygoid is very small, as 
in the Marsupials, and this comes from the fact that what is generally, in the higher 
mainmals, the upper or basicranial flange, is here, as in the Marsupials, a long, tongue- 
shaped mesopterygoid (ms.pg.). This flat bone is sharp in front, where it wedges in 
