DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 269 
seen in the side view. Then the post-temporal and mastoid regions are concave, turn 
obliquely, and are swollen and sinuous, with the great air-cells within, which are well- 
marked on the outside, every cell marking its own convexity. The supraoccipital 
ridges, vertical and transverse, can be seen in this view, and the large projecting 
occipital condyle. 
The end view (Plate 39, fig. 4) shows the gently hollow sagittal region (7.p.) ; the 
outspread, foliaceous postorbitals (p.o.); the widely extended glenoidal part of the 
squamosals (sq.); the post-temporal region of the same bones, overlapping the mas- 
toids (op.); the projections further forwards of the postglenoid ridges, and the free 
fore legs of the tympanic (a.ty.). The large foramen magnum is seen to be somewhat 
elliptical, with the long axis transverse; over it the supraoccipital forms a low arch, 
and on that bone, above, there is a keel, derived first from the interparietal ; and from 
the top of the keel or crest a transverse ridge, right and left, enclosing the supra- 
occipital region. 
The very large condyloid foramina (XII.) are well seen inside the foramen magnum, 
in front of the large subpedunculate condyles ; then the occipital arch is constricted, 
and the paroccipital ridges are obsolete, but the mastoid grows inwards over that 
region, and forms a thin-edged floor to the passage for the 9th and 10th nerves. The 
general form of the great hard palate in the adult is oblongo-elliptical, and it is 
half the length of the whole basal tract. The anterior palatine foramina are large 
and oval, the posterior palatine foramina are moderate, far back, and far apart, lying 
in the fossa of the palatine plate of the palatines, close to the junction of these bones 
with the maxillaries. 
The general surface of the hard palate is gently hollow, margined by the edentulous 
part of the narrow premaxillaries, in front, by the large sockets and teeth laterally, 
and by the exquisitely wrought, thickened and ribbed edge of the narrow palatines, 
behind. These plates grow backwards to receive the crest of the vomer, and then 
arching forwards, run round the posterior nares, curving in again to form a waist in 
the open part, and then ending in a sharp ridge, turned outwards, which ends in the 
small unciform external pterygoid process. Inside these alisphenoidal hooks there is 
a more delicate pair of hooks, the hamular processes of the pterygoids. The hinder 
edge of each pterygoid is notched above the hook, and then runs backwards and 
outwards in a sharp ridge, reaching the foramen ovale. The keel of the vomer ends 
between the pterygoids; then the skull is made carinate by the slender acicular 
parasphenord, is then gently convex along the middle, and becomes subcarinate in 
front of the foramen magnum. 
The transverse well-margined glenoid cavities, underlapped behind by the thick 
incurved postglenoid process, might belong to some stout Carnivore. 
The neat foramen ovale lies between the glenoid facet and the cranial part of the 
pterygoid ; behind and inside it is the ragged opening of the Eustachian tube, floored 
by the sharp, rough fore lip of the tympanic bone. The keeled bottom of the deep, 
MDCCCLXXXV. 2M 
