40 ] 
RECORDS OF W.A. MUSEUM. 
nearest to those of the former, the mandible showing characters 
common to the two, while the cheek-teeth are of the type of the 
latter. 
It is easy to see how the structure of the cheek-teeth could 
pass into that of the Phascolomyidce ; and it is not improbable that 
the two families may have diverged from a common ancestor. 
The structure of the humerus apparently indicates fossorial 
habits.” 
Two teeth from the upper jaw of a large Diprotodontoid 
marsupial were obtained from the lower stratum.* The one tooth 
is a premolar and the other a molar. They both belong to the 
left series. 
The bilobed molar (plate vi., figs. 8 and 9) has a rhomboidal 
outline, narrower posteriorly, with the angles obtusely rounded ; the 
anterior surface and the sides measure from 35 to 36mm. in linear 
extent, the length of the posterior face is 32mm. 
The two lobes of the tooth are parallel and en echelon, the hind 
lobe projects farther inwards and is rather shorter and narrower ; 
each lobe shows a slight swelling at the inner extremity, is convex 
on the anterior face and concave backwards. The crest of each 
lobe is obliquely truncated, the exposed dentine sloping anteriorly. 
As the fore lobe is more worn than the hind one it has developed 
a larger tract of bared dentine. 
Distinct anterior and posterior basal ridges are present, each 
terminates in a tuberosity at its outer end, and does not ascend the 
outer side of the lobe. The posterior ridge and tuberosity are less 
developed than the anterior ones. The inner continuation of the 
anterior basal ridge ascends the interior face of the lobe, gradually 
diminishing as it approaches the summit, on the posterior face of 
this lobe it descends to form a ridge closing the inner end of the 
mid valley, it then rises on the fore side of the hind lobe, subsiding 
towards the summit. A continuation of the posterior basal ridge 
rises upon the interior face of the hind lobe. On the outer aspect 
of the tooth a distinct isolated ridge closes the outer end of the mid 
valley. 
1 Ante p. 12. 
