PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
201 
part of the skeleton in the Bird, and similarly relates to the faculty of station and pro- 
gression on the hind pair of limbs — the movement being, in the Kangaroo, as in some 
tribes of birds, by a series of hops, the fore limbs, however, in the mammal taking also 
an occasional share in progression on land, which is not permitted to the volant 
class. 
The portion of pelvis (Plate 22) corresponding in size with the sacrum (Plate 21), 
although reduced to the parts immediately surrounding the acetabulum, includes the 
base of the ilium, showing its three-sided prismatic form, the precotylar tuberosity, and, 
above all, the “ pectineal process ” (ib. e), in size, shape, and position closely corre- 
sponding with that in Macropus rufus f . 
The anterior or hremal facet of the ilium (ib. fig. 1, 62 ) is more deeply excavated than 
in the recent Kangaroo ; the rounded angle (d) dividing that facet from the inner or 
median facet (ib. fig. 2, 62 ') is relatively thicker. The precotylar tuberosity ( d ) is more 
prominent, is relatively nearer the acetabulum ; and a ridge is continued from the fore 
part of the tuberosity to the brim of that cavity, which more definitely or abruptly 
there defines the haemal from the neural facets of the ilium than in recent Kangaroos. 
The contour of the acetabulum is more ovate, the smaller end, at the fore part of the 
brim, being narrower in the larger fossil. The notch ( y ) at the hind part of the brim 
is narrower, and is nearly bridged over by the extension of the ischial (63*) toward the 
pubic (64*) border of the notch; the depression ( x ) into which the notch expands at 
the bottom of the cup is relatively narrower in Palorchestes than in Macropus. 
These characters would have indicated specific distinction if the present fossil had 
not exceeded in size the corresponding part in the largest living Kangaroos ; the degree 
to which Palorchestes surpassed them is exemplified in the pelvis as in the skull. 
Admeasurements of Pelvis. 
Palorchestes. Macropus rufus. 
Breadth of haemal surface of ilium above the precotylar in. lines. in. lines. 
tuberosity 30 10 
Breadth of neural surface of ilium above the precotylar 
tuberosity 33 13 
Breadth of median surface of ilium below symphysial 
surface 20 10 
Length of acetabulum 28 17 
Breadth of acetabulum 26 14 
Breadth of ischium behind the lower part of acetabulum .22 13 
§ 5. Palorchestes (Femur). — The fossil thigh-bone, of which the two extremities are 
figured in Plate 23. figs. 1 & 2, shows an articular head («) fitting the acetabulum of 
the pelvic fossil (§ 4). The height of the trochanter major ( f ), the length and back- 
ward position of the narrow trochanter minor (n), the depth of the cavity (l) under- 
t Mem. cit. Trans. Zool. Soc. vol. ix. plates lxxix., lxxx., e. 
