LIASSIC FORMATIONS. 
27 
between the temporal fossae, and a continuation of the same crest, whose sides slope 
away from each other at a right angle, characterises the upper part of the frontal to 
midway between the orbits. The postfrontal bar, or flattened tract, dividing the 
orbital from the temporal fossae, is an inch in breadth. The narrow nasals are 
divided by a medial suture, and, with the prefrontal and lacrymal, separate the 
orbit from the nostril. 
The lower jaw has slipped from beneath the cranium, and, by the effect of 
the gradual pressure, has been turned, with the flatter left side upward. The angle 
projects beyond the articular surface 2 inches 3 lines, terminating obtusely, slightly 
bent, with the concavity upward, and 1 inch in thickness. The great part of the 
articular cavity of the right ramus is exposed, showing a transverse diameter of 1 inch 
3 lines, and a fore-and-aft diameter of 10 lines: it is concave lengthwise, sinuous 
across. In advance of the articulation the ramus shows a depth of 1^ inch, gradually 
increasing to that of 2 inches 3 lines, and then contracting vertically toward the 
dentary part ; the deepest portion, formed by the angular and sub-angular elements, is 
situated about four inches in advance of the articular cavity, and there the thin outer 
parietes of the ramus have been crushed in, yielding to the superincumbent pressure. 
The length of the dentigerous part of the jaw is 1 foot 2 inches ; externally the 
dentary descends vertically from the sockets containing the teeth, but internally it 
swells out into a strong, convex, longitudinal tract, strengthening the alveoli, until the 
two dentaries meet at the symphysis. There is a longitudinal groove at the middle 
of the inner surface, below which the bone again swells out and is continued into the 
thick under surface of the dentary. The length of the symphysis is nearly 7 inches ; 
and here the vertical extent increases, and terminates more sharply below. The 
vertical extent of the dentary, behind the symphysis, is 1 inch, the deepest part of the 
symphysis is 1^ inch ; the outer surface of the symphysis is coarsely and irregularly 
rugose ; its upper border is scooped out at the alveoli for the larger teeth ; on the left 
side there are about twenty-two sockets for teeth of different sizes j the smallest are 
behind, and the hindmost shows a straight crown (Tab. IX, fig. 6), sloping forward, 
from 4 to 5 lines long, with the usual longitudinal ridges of the enamel. The tooth 
in advance is slightly bent ; the eighth in advance shows a crown, 9 lines in length ; 
the fifteenth in advance (Tab. IX, fig. 4) shows a sudden increase of size, and greater 
degree of backward curvature ; including this, eight teeth occupy the rest of the 
alveolar surface, which is coextensive with the symphysis. Here the teeth are divided 
by intervals of rather more than their own basal breadth ; the largest tooth (ib., 
fig. 3), following the curvature, has a crown two inches in length. The longitudinal 
enamel-ridges begin at from one to two lines above the base of that covering of the 
crown, where it is smooth, and they terminate about the same distance from the apex ; 
they are least developed at the outer, convex part of the upper half of the crown. 
Two of these large, laniary teeth project from the anterior alveolus, the outer and 
