io 4) 
PROF. OWEN ON A MANDIBLE AND 
These indications of a distinct species are supplemented by characters of the man- 
dible itself. 
In Palorchestes azael' the inner plate of the ramus descends from the alveolar margin 
of m1 and m2 with a very feeble convexity, soon changing to as slight a concavity, 
until this is lost in the beginning of the convex sweep round the lower border of the 
ramus. The initial convexity from the inner border of the alveolus of m3 in P. azael 
is but little augmented, and soon passes into a rather deeper concavity, closed by the 
beginning of the inflection of the angular part of the ramus. A tendency to a smooth 
flatness characterizes all the inner plate of the ramus descending from the molar alveoli 
to the lower vertical convexity. 
In Palorchestes crassus the inner wall of the ramus below m1 describes a moderate 
but uninterrupted convexity as it descends to the lower border; and this convexity 
increases below m2 and m3 before changing to the concavity (fig. 2, a) indicative of 
the characteristic marsupial inflection of the hinder third of the lower border of the 
ramus. 
The depth of the ramus below the fore part of m1 in P. crassus is 2 inches 10 lines, 
that behind m3 is 3 inches; the corresponding admeasurements in P. azael are 
3 inches 2 lines, and 2 inches 7 lines. ‘The depth, or vertical extent, of the ramus 
augments as the jaw extends forward along the molar series, in P. azael (op. cit. Plate 
evi. fig. 1), but diminishes in P. crassus (Pl. II. figs. 1 & 2); and this diminution seems to 
have been greater below d 4, instead of the increase of depth there shown in P. azael. 
The tooth d4, in P. azael, is broken away in P. crassus; but the extent of its 
alveolus is traceable. A vertical line dropped from its fore part crosses the hind part 
of the symphysis mandibuli (Pl. II. fig. 2, s), but does not reach so far in P. azael. In 
this species the symphysis begins in advance of such line. 
A greater proportion of the symphysial part of the mandible and of the right ramus 
is preserved in the subject of the present paper than in that of P. azael*. The sym- 
physial joint (PI. II. fig. 3) is obliterated by confluence there of both rami, a con- 
dition I have not noted in any other Macropodal genus. Some approach thereto is 
shown in a fossil mandible of the largest species of Procoptodon. In that, e. g., of 
P. goliah, described in the before-cited work *, I note: —'Lhe symphysis is continued, 
broadly, to the incisive outlets; it has assured, apparently, an attachment to each 
other of the rami of this instructive mandible, too intimate to be disturbed by 
posthumous movements, although ankylosis has not been completed, if it had 
commenced.” 
In the present mandible of a still larger Kangaroo that ankylosis is as complete as 
* Researches on the Fossil Remains of the Extinct Mammals of Australia, 4to, yol. i. (1877) p. 465, 
pls. cy.-evii. 
* Op. cit. vol. ii. pl. evi. fig. 1. * Researches on Foss. Mamm. Australia, vol. i. (1877) p. 464. 
