790 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
of the ramus, a nearer approach to the characters of Nototherium than is shown in 
any of the foregoing extinct genera of the Macropodal group of Marsupialia. 
What is wanting in the above-described fragment of jaw with the small proportion 
of dentition, by which is indicated a second species of Procoptodon , has been supplied 
by a plaster cast and photographs of an almost entire right ramus, with the molar series. 
The complex characters of the hindmost and least worn teeth (Plate LXXVIII. fig. 3, 
m 2, m 3) unmistakably repeat the generic type of those of the upper molars of Procop- 
todon Pusio (Plate LXXVII. fig. 7) ; but the difference of dimension is, to my experi- 
ence, specific ; and since it is in degree that shown by the premolar germ in the fragment 
of immature jaw (Plate I^XXVII. fig. 8), I regard the specimen in the Sydney Museum, 
from which the cast and photographs were taken, as part of a mandible of a mature 
individual of Procoptodon Bapha. The longitudinal extent of the upper molars (d \-m 3) 
in Proc. Pusio is 2 inches 6 lines ; that of their homotypes in the mandible of Proc. 
Raplia is 3 inches. The breadth of these lower molars similarly exceeds that of the 
upper ones in the subjects of Plate LXXVII. figs. 6, 7, which is fatal to the hypothesis 
of those of Plate LXXVIII. belonging to the same species. 
The mandibular ramus of Procoptodon Eapha is short, straight, deep, and thick, in 
the latter dimension (fig. 3) increasing from the symphysis to the ascending branch 
more gradually but to a greater extent than in preceding genera of Kangaroos. The 
lower border is convex across, thickest behind the symphysis, and suddenly becomes 
thinner at its hinder third (ib. fig. 2, d , d'), where a longitudinal channel (ib. b') along 
its inner side gives it the appearance of being slightly inflected that way ; but the 
channel ( b ') is interrupted by a more sudden or direct inflection of the proper “ angle of 
the jaw” (ib. a), which here, as in the other macropodal fossils, has been broken away. 
The fore border of the symphysial end of the ramus bends up at about an angle of 
135° with the axis of the mandible. On the outer side (ib. fig. 1) the alveolar tract is 
impressed by an irregular longitudinal moderately deep channel, below which the bone 
swells out and the vertical convexity to the lower border augments from below the 
first molar (p 3) to the origin of the coronoid process ( q ). A little way behind the ante- 
rior border of this process it is feebly impressed, or the surface subsides; but the low 
rough ridge (fig. 1, h ), indicative of the lower boundary of the ectocrotaphyte fossa, is 
at a higher level. 
The ramus gains slightly in depth or vertical extent from the groove (b 1 , fig. 2) to the 
symphysis (s, s'). The articular syndesmotic surface is broad, strongly roughened and 
sculptured, and extends from the lower border of the ramus (s) to the outlet of the 
incisor ( i ) ; the hind border of the symphysial surface is feebly impressed, as in Phasco- 
lomys (Philosophical Transactions, 1872, Plate xxi.). 
The union of the two rami must have been firm, not admitting of any reciprocal move- 
ment ; indeed the fore part of the joint had become obliterated by anchylosis, and part 
of the left ramus is here adherent in the fossil. The inner surface of the ramus is 
almost flat to where it bends to the under border ; the narrow continuation forward of 
