626 MR. P. D. MONTAGUE ON THE 
enabled the writer, accompanied by Mr. L. Burns, of Perth, W.A., 
as assistant, to spend from May 29th to August 29th, 1912, 
collecting upon the islands. Mr. Burns has since been drowned 
while duck-shooting at the Forrest River, near Wyndham. He 
was a very able collector and a delightful companion. 
I must here acknowledge the very great assistance received 
from Professor Stanley Gardiner at home, from Mr. Woodward 
and Mr. W. B. Alexander in Western Australia, and from 
Mr. Gregory Mathews and workers in various departments of 
the British Museum (Natural History), who have so kindly helped 
in identifying the specimens. 
A detailed description of a local fauna is incomplete without 
some account of its environment; it is therefore necessary to 
consider the prevailing physical conditions and geographical 
features of the locality before proceeding to an account of the 
various forms inhabiting it. 
The group lies approximately in lat. 20° 25’ S., long. 115° 30! E., 
105 miles E.N.E. of North-West Cape, and 40 miles from the 
mouth of the Fortescue River—the nearest point on the main- 
land. It is near this latitude that the rainfall on the West 
Australian coastal region reaches its minimum, averaging under 
8 inches per annum; it is of very irregular occurrence, droughts of 
two or even three consecutive years being not infrequent. The 
rain falls in the summer, usually in January or February, and is 
frequently attended by a particularly severe form of’ eyclone 
known locally as a ‘ Willi-willi.” These storms strike the West 
Australian coast between latitudes 18° and 23°, and cause much 
destruction to buildings and shipping. Their wind velocity has 
never been accurately measured, but lines of short iron telegraph- 
poles bent in the middle through as much as 45° testify to the 
force attained. Cyclones may occur between November and 
March; from mid-April until October, comparatively calm and 
dry weather may be depended upon. During these months there 
are occasional winter showers, which become more frequent and 
regulay further from the coast. Hence the islands are favoured 
with’ a slightly higher rainfall, and the vegetation is in conse- 
quence a little more luxuriant and less scattered than that of the 
mainland in the corresponding latitude. Though these showers 
are refreshing when they do occur, they are really very scanty, 
and contribute but little to the average, for the bulk of the rain 
falls in one or more tropical downpours during the course of a 
few hours. 
The temperature is not excessive; during our visit the shade 
temperature at mid-day averaged 82°3°, never rising above 
90-0° F. 
The geological formation throughout is of sandy post-tertiary 
limestone, similar to that of the mainland, which extends in an 
interrupted belt down the greater length of the west coast of the 
continent, and is supposed to have accumulated by wind-action. 
