220 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
The shaft of the great metatarsal of Palorchestes is subtrihedral ; the rotular surface 
(ib. fig. 1, iv) is slightly concave transversely along its middle third as in Macropus 
Titan , not prominent as in Macropus rufus (ib. fib. 4). The plantar side (ib. fig. 2) is 
produced into a ridge, broad along the upper third (o), becoming sharper (h, h) as it 
descends, and subsiding about one half of the length of the bone (o') from the distal 
end. The corresponding portion of the metatarsal of Macropus rufus (ib. fig. 6) is 
widely channelled where in the fossil it is angularly convex. The greatest rotulo- 
plantar thickness of the shaft in Palorchestes is 1 inch 4 lines, the greatest transverse 
thickness is 1 inch; that of the proximal end is 1 inch 6 lines, its rotulo-plantar thick- 
ness is 1 inch 5 lines. 
The fifth metatarsal of Palorchestes Azael (Plate 29. figs. 1, 2, 3, v) is relatively much 
stronger than in Macropus major or Macr. rufus (ib. fig. 4, v). The plantar part of the 
proximal end, broken away in the fossil figured, is entire in a later acquired homologous 
bone of Palorchestes. This presents a small, oval, flat, vertical surface for the fourth 
metatarsal, a broader subtriangular one for the backwardly extended process of the 
cuboid*, and a larger horizontal facet for the surface, marked Zf, of the same tarsal 
bone. The proximal articular surface of the fifth metatarsal is very small in propor- 
tion to the bone in Palorchestes. External (fibulad) to that surface the bone rises above 
the proximal end of the fourth metatarsal in the form of an antero-posteriorly extended 
thick round edge. 
The shaft of the fifth metatarsal is subcompressed along the proximal three fourths ; 
it measures 13 lines in rotulo-plantar thickness, one third down ; and here, near the 
plantar side, its thickness (or tibio-fibular breadth) is 6 lines. The opposite (rotular) 
border is not sharp, as in Macropus major and Macr. rufus ; but though thin, in com- 
parison with the plantar surface, the border is rounded off. The shaft loses rotulo- 
plantar thickness and gains transverse breadth as it approaches the trochlear articular 
surface (v); this is 1 inch transversely, 10 lines where thickest from before backward. 
The surface is not simply convex, as in Macropus rufus (Plate 29. figs. 4 & 5, v), but is 
made trochlear by a plantar median ridge, on each side of which the surface, trans- 
versely, is feebly concave. The outer (fibular) side of the shaft has a feeble median 
longitudinal channel along the middle of the proximal two thirds. The upper half of 
the shaft shows in fractured portions of homologous fossils a small medullary cavity. 
Thus we learn that in the large extinct Kangaroo of the genus Palorchestes the 
fourth and fifth digits were less unequal in strength, and the fifth took more share in 
station and locomotion than in the largest existing kinds. The metacarpal segment 
and the rest of the foot were proportionally broader; but the length of the fourth 
metatarsal in Palorchestes indicates, nevertheless, that it was a powerful leaper. 
§ 15. Procoptodon (Metatarsal and Femoral Characters). — In deprecation of the fore- 
going details, more wearisome perhaps to the reader than the inditer, I may plead the 
* “ Osteology of Marsupialia,” Zool. Trans, tom. cit. plate lxxxiii. fig. 11, Jc. 
f Ibid. fig. 10. 
