-FROM SOUTH AFRICA AND AUSTRALIA 123. 
On the left side, the bones which should constitute the lower end 
of the mandibular suspensorium have almost entirely disappeared, a 
small fragment only of the quadratum remaining. On the right side, 
however, a considerable proportion of the quadratum is preserved 
(Pl XNI. [Plate 7] fig. 4). Its articular end, ;';ths of an inch 
broad, and flattened from above downwards, exhibits a condyloid 
surface which is divided by a groove into a stronger internal, and a 
less prominent external portion. In front of the condyles the quad- 
ratum is very thin, but it rapidly expands, so as to cover all that 
remains of the flat lateral face of the suspensorium, and extends for- 
ward to about midway between the articular condyle for the mandible 
and the posterior margin of the orbit. At this point the bony matter 
disappears. On the top of the skull all the osseous matter has 
vanished except two white lines, one on each side of the interorbital 
space (representing the upper edges of the orbito-sphenoids?), and a 
sinuous transverse line faintly indicating the contour of the occiput 
(PI. XXI. [Plate 7] fig. 1). 
The lower jaw (figs. 2, 4, 5) has the same general outline as the 
anterior and lateral contours of the skull. Its rami are slender in. 
front, but deep and strong posteriorly, where there is a faint indica- 
tion of a coronoid elevation, in correspondence with which the 
inferior margin of the suspensorial peduncle is slightly excavated. 
Behind this the ramus rapidly narrows to its posterior extremity, 
which extends very little beyond that of the quadrate bone. At the 
symphysis, the dentary element of the mandible is very distinct and 
is rather less than 3th of an inch in width; it extends back, becoming 
more slender as it goes, along the upper edge of the mandible. Its 
posterior boundary cannot be exactly traced; but the backward 
continuation of the series of teeth with which it is beset testifies to. 
its elongation beyond the level of the posterior margin of the orbit. 
The symphysial end of each dentary bone is concave and produced 
into a short process posteriorly, so that the union of the two rami 
would seem to have been somewhat lax (fig. 3). 
The counterpart of the fossil (figs. 1, 2, 3) just described exhibits 
the dentary bone of the right ramus in transverse section. It is 
triangular, with a thin internal edge and a flat upper surface. The 
teeth are set in apparently distinct alveoli along its outer moiety ; 
and beneath them runs a canal filled with matrix. 
A second osseous element of the mandible, the angular bone, 
extends on the inner side of the jaw to within 7%ths of an inch of 
the symphysis. It is trough-like (fig. 5), consisting of an internal 
and an external lamella, united at an angle below, and it appears to. 
