682 On a new Rock-Wallaby. 
By its general characters the animal is clearly related to 
the West Australian Petrogale lateralis of the Swan River 
district and to P. hacketti of Mondrain Island. his latter 
was described as a subspecies of P. lateralis, but I should 
ow give it specific rauk on account of its uniformly larger 
size and certain differences in the structure of its skull. 
The new form is thus situated far to the east of the pre- 
viously known members of the group, with the large hacketti 
between it and the form which it—at least superficially— 
most resembles. 
It may be called 
Petrogale pearsoni, sp. n. 
Size comparatively small, about as in lateralis, decidedly 
smaller than in hacketti. General colour, on the whole, very 
much as in lateralis, paler than in hackett/, Dark lateral 
lines of the underside, however, more blackish, those of 
lateralis being dark brown, White patches at base of ears 
larger and more prominent. ‘Tail with its upper and under 
surfaces, from about 3 inches from the base, contrasted 
black, the sides dull buffy whitish ; above, the black soon 
fades off into the brownish terminal tuft, but below it con- 
tinues to within 2 inches of the tip. This tail-coloration is, 
on the whole, more as in hacketéid than lateral’s, but in both 
there is considerable variation. 
The usual narrow black dorsal line is continued rather 
more definitely on to the rump than in any of our specimens 
of lateralis, but the difference mi ay be due to this part being 
in fresh pelage, and so showing the line more distinctly. 
Skull in size and general shape quite as in lateralis, 
smaller and with less heavy supraorbital ridges than in hacketti. 
Palatal foramina comparatively long, about as long as in 
hacketti. In the bullse there is a difference between lateralis 
and hacketti which had not been previously noticed. In the 
former they are fairly well swollen, anteriorly as well as 
posteriorly, so as to produce a transverse convexity (hardly 
to be called a ridge), in front of which the bone descends 
nearly vertically towards the level of the glenoid surfaces. 
In hackelti, liowever, the whole bulla is larger, but lower 
and more spread out, its front part evenly and gradually 
descending towards the glenoid level without marked trans- 
verse convexity. In pearsont the bull are most like those 
of havkettt, although perhaps a little more swollen, In 
making this comparison six skulls of hacketéc and ten of 
lateralis have been available, so that the difference is evidently 
fairly constant, 
