1369. ] HUXLEY—HY PSILOPHODON. +) 
Upwards and backwards the same region of the premaxilla passes 
into its anterior ascending process, which is 0-7 inch long, and 
becomes very slender above. Each uniting by harmonia, but not 
ankylosing, with its fellow, the two lie between, and separate, the 
inner edges of the nasal bones for a certain distance. Behind the 
nasal aperture the preemaxilla rises into its posterior process, which 
is about as long as the anterior, but has a much greater breadth. The 
posterior margin of the process, and of the body of the bone below 
it, 1s concave, rounded, and must haye been quite loosely united 
with the anterior edge of the maxilla. 
Five teeth with lanceolate acuminated crowns (fig. 3) le close 
together in the premaxilla, occupying a distance of 0:55 inch from 
its posterior end; but the alveolar margin of the “beak,” which 
is continued in front of this, presents no indication of the pre- 
sence of teeth. The maxilla is imperfect behind. So much of it as 
remains measures 1:5 inch in length, and rather more than half 
an inch in depth, posteriorly, where it is deepest. It bears ten 
teeth. The crowns of the anterior eight are well preserved ; but 
the two hindermost are broken, only the section of the fang of the 
last being visible. The anterior four teeth are rather smaller 
than the others; and this is especially true of the first tooth. The 
anterior edge of the crown of each of these teeth slightly overlaps 
the posterior edge of the crown of its predecessor. In the fifth, 
sixth, seventh, and eighth teeth, the overlap seems to have taken 
place in the opposite direction, the hinder edge of each tooth pro- 
jecting a little beyond the anterior edge of its suecessor. The teeth 
are imbedded by single fangs, and, judging from the hindermost, are 
lodged in distinct alveoli. In unworn teeth the summit of the crown 
is sharp, and has a curved contour, which is more convex downwards 
in the anterior than in the posterior teeth. The free edge of the 
crown presents no trace of the serrations which are so characteristic 
of the teeth of Zyuanodon; but it is sinuated by the terminations of 
sundry strong ridges of the enamel (fig. 2), which start from a sort 
of cingulum at the junction of the crown with the fang and, some- 
what diverging and diminishing in thickness, traverse the outer 
surface of the crown. The cingulum is sharply angulated upwards 
in the three anterior teeth; but the angle becomes obtuse in the 
hinder teeth. The principal enamel ridge proceeds from the open 
angle of the cingulum, or a little behind it, to the crown. Secon- 
dary ridges of less prominence, which may not reach the cingulum, 
subdivide the spaces on each side of the principal ridge; and be- 
tween them there are still shorter tertiary ridges, which do not 
extend more than halfway from the free edge towards the fang of 
the tooth. The sixth tooth is that the crown of which is most worn 
down, the other teeth being to all appearance less worn as they are 
further from it. The planes of the worn surface of the crowns, as 
in Jguanodon, cut the axis of the tooth at an acute angle, looking in- 
wards as well as downwards. The outer contours of the teeth are con- 
vex from above downwards, but hardly so much so as in Jguanodon. 
At first sight, these teeth look very similar to those of Zguanodon ; 
