PROFESSOR OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
219 
Plate 29. fig. 1, is two thirds that of the same part of the femur, as shown at the 
broken ends in figs. 1 & 2 of Plate 23. The breadth of the naturally united fourth and 
fifth metatarsals (Plate 29. figs. 1 & 2), one third from their proximal ends, equals four 
fifths of the same -part of the femur of Palorchestes Azael. 
To this species, therefore, I provisionally refer the fossil subjects of figs. 1, 2, and 3 of 
Plate 29. The length of the fourth metatarsal in those figures is restored in outline 
from an entire homologous bone of the same extinct species which had become detached 
from the contiguous metatarsals, and which I have not thought necessary to figure. 
In the fossil under description, to the great fourth metatarsal lacking the distal end 
there remained attached the fifth metatarsal (ib. figs. 1 & 2, v), wanting only a portion 
of the plantar or posterior wall of the proximal end ; and, similarly attached, the 
proximal half of the third metatarsal (ib. ib. ill), exhibiting the characteristic macro- 
podal slenderness. It is interesting to note, however, that the fifth metatarsal in the 
huge extinct Kangaroo shows more nearly the normal proportions of the bone than in 
the existing species, even the largest, as, e. g., Macropus ntfus (Plate 29. fig. 4, v); and 
the more slender third metatarsal bone of Palorchestes (hi, fig. 2, Plate 29) is relatively 
less atrophied than in existing Kangaroos. Its proximal end (ib. fig. 3, hi) presents an 
oblong, subquadrate, almost flat surface for the ectocuneiforin, and a triangular surface 
on the inner side (ib. fig. 2, h) of the proximal end for part of the head of the second 
metatarsal, which bone is wanting in the fossil. It articulates with the tibial side of the 
proximal end of the fourth metatarsal by a surface which is extended by the backwardly 
directed process (ib. fig. 2 , c). Below the articular head (ib. a-c ) the shaft narrows and 
becomes compressed in its upper third, below which it assumes a subtrihedral figure, 
with a trenchant margin both before and behind along its upper fourth. 
The shaft does not exceed 2 lines in breadth at the point of fracture (d). The bone 
closely adheres, either by anchylosis or matrix, to the shaft of the great fourth meta- 
tarsal, inclining from the inner (tibial) side to the plantar aspect of the shaft, as does 
the corresponding metatarsal in Macropus rufus *. The proximal articular surface of 
the fourth metatarsal (Plate 29. fig. 3, iv) presents an undulating tract adapted to the 
distal surface of the cuboid ; its broadest rotular (anterior) half is gently convex trans- 
versely at the fibular half, concave at the tibial half; the narrower plantar or posterior 
subquadrate tract is feebly concave rotulo-plantad, almost level transversely ; this tract 
extends plantad, or backward, so as to overhang the shaft ; it is grooved at e, fig. 3, by 
the “ peroneus ” tendon, which runs across the back or under (plantar) aspect of the 
tarsus to be inserted into the entocuneiform bone ; also, as in existing Kangaroos and 
in Macropus affinis , it has a fiat articular surface at the underside of the overhanging 
part for the large tarsal sesamoid. The inner or tibial side of the proximal end of the 
fourth metatarsal shows the two small vertical facets for the ectocuneiform, and a well- 
marked rough depression for the proximal ends of the third and second slender 
metatarsals. 
* Zool. Trans, tom. cit. plate lxxxiii. fig. 1, in. 
2 H 
MDCCCLXXVI. 
