131 
FIBULA. 
The mutilation of both ends of the only bone obtained of this 
kind precludes satisfactory measurement or description. 
ASTRAGALUS. 
| One complete specimen. | 
The Astragalus presents a combination of phascolomydian and 
diprotodontoid features with a preponderance of the latter. 
It shares the generally depressed characters of the head of this 
bone in the wombat, but whereas, in the latter, the anterior 
articular convexity for the navicular is coincident with the whole 
anterior transverse width of the bone, there is, in Phascolonus as 
in Diprotodon, a non-articular tract to the outside of that part 
which represents the head. Though less conspicuously than in 
Diprotodon the internal border of the superior surface is, in the 
same kind of way, elevated into a low pyramidal or conical pro- 
jection but, unlike the condition which obtains in Diprotodon, 
the inner side of this is partly articular, being in opposition 
with the limited portion of the astragalar surface of the tibia 
that has been mentioned as extending on to the outer surface of 
the internal malleolus. This small tract on the inner side of the 
projection is the only representative of the extensive surface 
that, in the wombat, articulates extensively with the internal 
malleolus. 
In both Diprotodon and Phascolomys latifrons the articular 
surface of the head of the astragalus and of its tibial surface are 
discontinuous by the intervention of a non-articular tract but in 
Phascolonus the two are continuous by an extension of the latter 
which meets the former. 
A feature of the astragalus of Phascolonus, not found in 
Diprotodon in which the tibial surface is remarkably flat, is a 
certain amount of elevation of the border of its antero-external 
region ; thus the slope, inwards, from this raised edge and the 
opposing slope, outwards, from the previously described pyramidal 
elevation of the inner border produce a marked concavity 
between these two elevations. 
The continuous articular tract on the external aspect for the 
fibula and pyramidalis is, as in the wombat, also directly con- 
tinuous, though at a less acute angle, with the calcaneal surface 
of the bone; in Diprotodon the two are separated by an inter- 
vening non-articular strip. 
On the under side the features of the astragalus present a 
considerable resemblance to those of the corresponding surface in 
Diprotodon, the principal difference being in respect of the 
relatively large non-articular tract which, in Phascolonus, is left 
n the postero-internal region. 
