526 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
the outer border of the first projects further from the midline than does that of the last. 
Viewed from the palatal aspect the two series of incisive alveoli converge backward, 
instead of forward as in the Kangaroo and most other quadrupeds. The malar bone 
(Plate XXXV. fig. 1, 26 ) ascends from its junction with the maxillary to join the lacrymal 
(73) at the fore part of the orbit, by a very narrow curved strip or process ; its main body 
is suspended in the zygomatic arch, of which it constitutes the anterior half, and the 
lower part, as far as, and including, the “ eminentia articularis.” The suture between 
the squamosal and malar elements of the zygoma is almost straight, extending from 
behind the orbit obliquely backward and downward to the glenoid cavity, of which 
articular surface the malar “ eminentia,” here more flattened than usual, contributes the 
fore part. This articulation (ib. fig. 4) is most extended transversely to the skull’s axis ; 
its hinder half (ib. ib. 27) is concave from before backward, its fore part (ib. ib. 26) 
convex, but becomes flattened or a little hollowed on the “ eminentia.” 
The lacrymal (ib. fig. 1, 73) is perforated by the canal, marsupial-wise, in advance of 
and external to the orbital cavity. 
§ 3. Mandible . — A transversely extended subconvex condyle (Plate XLII. figs. 3 & 4) 
adapts itself to the cavity offered by the base of the zygoma. The condyle is 5|- inches 
in transverse extent, 1 inch 9 lines from before backward ; it is, in that direction, most 
convex. The condyloid process is supported by a three-sided neck quickly contracting 
to 1 inch 9 lines in transverse diameter (ib. fig. 3, n ) ; it is broadest and flattened behind, 
contracted in front to the ridge-like beginning of the “ coronoid ” plate (ib. figs. 2 & 4 , r), 
which extends forward near the outer side of the neck. The condyle is more extended 
inward (ib. fig. 4, c) than outward (ib. ib. c') of this advancing vertical coronoid plate. 
The flat surface at the back part of the neck is continued into a suddenly expanded 
hinder facet of the ascending ramus, formed by the outward production of the hind 
wall or boundary of the outer depression for the insertion of the temporal muscle, and 
by the inward production (Plate XXXV. fig. 3, e) of the hind wall or boundary of the 
deep inner concavity of the ascending ramus, where opens the large entry (Plate XLII. 
fig. 2, 0 ) of the dental canal. Below this orifice the concavity extends downward through 
the concomitant extension of the inner plate or hind wall to the lower border of the 
horizontal ramus, where it gradually subsides. The hind wall of the outer depression 
of the ascending ramus (Plate XXXV. fig. 1, e) follows the contour of that of the inner 
depression, but sooner subsides; the interspace is a continuation of the broad hind 
flattened facet which, as it descends, gets a more outward aspect. Beyond the sub- 
sidence of the outer plate it gives the appearance of a bending inward of the angle of 
the jaw (ib. fig. 2, e'), and that to a degree which is characteristic of Marsupials. The 
outer or crotaphyte depression of the ascending ramus (Plate XXXV. fig. 1, /’) gradually 
gains the ordinary level of the outer surface of the horizontal ramus, and does not 
undermine the ascending branch to communicate with the inner concavity as in Macro- 
pus. In the shape of the condyle Diprotodon resembles Phascolomys , in which the 
intercommunicating canal is much reduced. 
