10 
DESCRIPTION OF PSEUDOMYS NOVAE-HOLLANDIAE 
palatal foramina, 4 3 mm. ; breadth outside M^, 5 5 mm. ; breadth inside M^, 
2'5 mm.; upper molars, 3 5 mm. 
Pseudomys hermamishiirgensis was described by Waite (1) 
from specimens taken on the Horn Expedition to Central 
Australia in 1895. In 1932 Trongliton (2) described a sub- 
species, P. Ii,ermannshurgciisis holami, from Ooldea, South 
Australia, its distinguishing characters being longer feet and 
ears, and less wtirm colouration. 
Amongst the Murinae in the National Museum are about 
100 specimens of this species, a little more than half of which 
were collected at Ooldea. The remainder are from Hermanns- 
burg (co-types), Charlotte Waters, Barrow Creek and un- 
specified localities in Central Australia. Amongst this large 
number there is a good deal of variation in general size, and 
in the length of ear, pes and tail. So generalized is it, how- 
ever, that it is impossililc to correlate the mice into geographi- 
cal races. Groups of mice, taken in the same place at the same 
time, show up to three millimetres difference in length of ear 
and pes, and f i*oni the same locality an earlier or later collec- 
tion may similarly vary around a smaller or larger general 
average. The cause of this variation is the irregular rainfall, 
which is an outstanding feature of the arid regions of Aus- 
tralia. After several years of drought the mammal popula- 
tion is poor and stunted. With good rain conies an abundance 
of food, fertility increases and young born during this period 
grow to larger proportions. 
The following figures are based on measurements of adults, 
Species 
Speci- 
mens 
measured 
HIND FOOT 
EAR 
TAIL (expressed 
as per cent, of head 
and body) 
variation 
mm. 
average 
mm. 
variation 
mm. 
average 
mm. 
variation 
average 
hermanns- 
burgensis 
Central 
Australia 
23 
15-5 
to 
19-5 
17-8 
12 
to 
16-5 
14 
101 fo 
to 
123% 
113% 
hermanns- 
burgensis 
South 
Australia 
32 
16-8 
to 
20 
18-3 
13 
to 
16-5 
14-6 
98% 
to 
150% 
112% 
novae- 
hollandiae 
19 
16-5 
to 
19-5 
18 
13-5 
to 
16-5 
14-9 
86% 
to 
111% 
100% 
