PROFESSOR OWEN ON THE EOSSIL MAMMALS OF AUSTRALIA. 
203 
At the distal end of the femur (ib. fig. 2) the chief distinction of Palorchestes from 
Macropus is in the relatively narrower postintercondylar fissure (u) and its minor ex- 
pansion, where it is closed anteriorly*. The depression (; y ) is strongly marked in 
Palorchestes. The epiphysial line is traceable in the fossil ; a wedge-shaped process at 
both the outer (z) and the inner (z 1 ) borders rises as if to clamp more securely the 
epiphysis to the shaft. 
The following admeasurements exemplify the difference of size between Palorchestes 
Azael and Macropus rufus, the measured femur of the latter being of a full-grown 
male : — 
Palorchestes Azael. Macropus rufus. 
in. lines. in. lines. 
Extreme breadth of proximal end of femur . . 
. 4 
9 
2 
9 
Extreme breadth of middle of shaft of femur . 
. 1 
8 
1 
0 
Extreme breadth of distal end of femur . . . 
. 3 
J 9 
2 
5 
§ 6. Palorchestes (Tibia). — If the fine fragment of this bone figured in Plate 24 be 
compared with the corresponding views of the entire tibia of the large male Red 
Kangaroo figured in vol. ix. of the ‘ Zoological Transactions,’ plate lxxxii., the associa- 
tion of the peculiar characteristics of the macropodal tibia with the grand proportions 
of that bone in Palorchestes will be readily appreciated. 
The length of the present fossil remnant from the proximal end of the bone to the 
subsidence on the shaft of the procnemial plate is 7^ inches. The fore-and-aft diameter 
of the tibia, at the upper part of the plate, is 3 inches 5 lines ; the span of the exca- 
vation between the procnemial and ectocnemial plates or ridges is 2 inches 4 lines ; 
the antero-posterior diameter of the head of the tibia is 3 inches 10 lines; the breadth 
of the back part of the tibia, at 5 inches below the articular head, is 1 inch 6 lines. 
The head of the tibia is in a state of epiphysis ; its undulatory course along the inner 
side of the bone is shown in fig. 4, but partial confluence, as in the case of the epi- 
physis of the femur of probably the same individual Palorchestes , has tended to retain 
the epiphysis in place, notwithstanding the movements and shocks of alluvial transport 
through which, seemingly, the fractures of the fossil are due. 
The inner articular facet (ib. fig. 5), the only one preserved on the head, is relatively 
more extensive and more concave transversely than in Macropus rufus. The hind 
surface of the shaft, continued down from that articular surface, is thicker and more 
convex across ; it contracts in the large recent Kangaroo to an angular ridge, sharply 
dividing the hinder from the antero-internal surface of the shaft of the bone. 
The following are a few comparative dimensions of the tibia : — 
* Compare fig. 2 with fig. 2, u ( Macropus rufus ) in plate lxxxi. of Mem. eit. Zool. Trans, vol. ix. 
2 P 
MDCCCLXXYI. 
