2 
HORN EXPEDITION—MAMMALIA. 
larger number of smaller and usually burrowing animals capable of living for long 
with very little water to drink, and able to feed upon insects such as ants or the 
piarched-up vegetation growing on the rocks and sand-hills. 
The fauna must also vary very much according to the succession of seasons. 
A year or two of drought will thin out the animal population to a wonderful 
extent, and this thinning out can only be made good again by increased fertility 
and by immigration following upon one or two good seasons. 
Anyone who has seen the central desert will realise at once how effectual a 
barrier to migration it affords to very many forms of life, the result being that a 
line of division can be drawn separating, as Professor Tate has pointed out, the 
Eremian remon of the centre from the Autochthonian in the south-west and the 
O 
Euronotian in the east and south-east. Around the true Eremian region runs a 
broad belt in the north, east, and south-east, over which the rainfall is less than 
twenty-five inches per annum. To the south-west lies a similar, only much 
narrower, band. To this matter reference will be made again when dealing with 
the marsupial fauna. 
Tlie mammalia of the central or Eremian region are representative of the five 
orders found elsewhere in Australia. 
(1) Carnivora. —The dingo {Canis dingo) is fairly numerous. Most of the 
specimens seen were of the yellow-brown colour, but occasionally they were black. 
We met with them everywhere, and they seem to wander far out into the sand-hill 
country, as one followed us at dusk across Lake Amadeus. Near to the latter the 
dead bodies of five were found polluting the water of a native well at the bottom 
of a hole some twelve feet deep, into which they had evidently ventured in search 
of water, and out of which they had been too weak to climb. They probably feed 
upon marsupials, such as the rat-kangaroo {Beftongia lesueuri), which is not rare 
upon the sand-hills. 
(2) Rodentia. —At certain times the country appears to be over-run by 
migratoi’y rats, who travel in vast hordes, appearing and disappearing with 
strange suddenness. At ordinary times perhaps the most common mammals are 
the small jerboa-rats (^Hapalotis mitchelli) and the mouse novce-hollandice ?). 
They are met with everywhere in the plain country. Though we did not meet 
with it, another species of Hapalotis i^H. conditor) has often been recorded from 
the central parts. This owes its specific name to the fact that one or two families 
construct a nest built out of sticks firmly put together in a somewhat beehive 
shape at the base of a shrub. 
