1909. |] FAUNA OF COCOS-KEELING ATOLL. 133 
an excellent account of their physical features in the Scottish 
Geographical Magazine (vol. v. 1889, pp. 281, 457 and 569), but 
he has not, so far as I am aware, published any description of the 
fauna. 
Since the atoll lies 12 degrees south of the Equator, it is of 
necessity subjected to some seasonal variations, and though these 
are greatly moderated by the influence of the South-East trade 
winds, they are sufticiently pronounced to affect the time of 
appearance of most of the insect fauna. It is therefore obvious, 
that a stay of a few days could not produce, even with the most 
industrious collecting, at all a representative series of the insect 
fauna. The present list need not therefore be taken as indicating 
that a great increase has taken place in the fauna within the past 
thirty years, for it is more properly an index of more protracted 
collecting at all seasons of the year’s cycle. 
The atoll consists of some two dozen typical ‘“ low ” islands, that 
rise but a few feet above mean tide-level, and enclose a lagoon 
some 8 miles in diameter. The whole group liesat 12°10°S., 96° 
52° E.; and is separated by upwards of six hundred miles from 
Java, and upwards of five hundred from Christmas Island, its 
nearest neighbour. 
In 1827 the atoll was settled by the pioneer member of the 
Clunies-Ross family, and ever since that time the destinies of the 
group have been swayed by three generations of the same family. 
The islands were uninhabited before the advent of the Clunies- 
Ross dynasty. In 1901 a Telegraph-station was erected on Pulu 
tikus, for the working of the cable between Perth (Australia) 
and Mauritius. 
The South-East trades blow for some three hundred days each 
year, and the climate is subject to no sudden changes save infre- 
quent cyclones; the mean temperature is 81° Fahr., and the 
annual rainfall averages something over 70 inches. 
MAMMALIA. 
The Rats of the atoll are of some interest, apart from their 
economical importance. When the original settlers arrived in the 
group in 1827, rats were already established on one of the islands, 
and this island was named Pulu tikus, or rat island, in con- 
sequence. 
From 1827 till 1878 these rats remained as the only repre- 
sentatives of their family, and continued to be almost confined to 
the island of their settlement. Towards the end of 1878 a ship, 
‘The Robert Portner, was wrecked in the atoll, and left as her 
legacy a flourishing colony of Mus decwmanus ; since then other 
wrecks, and trade intercourse, have added Mus rattus to the island 
fauna. The products of these separate invasions have remained 
distinct until to-day, and they have fairly sharply defined areas: 
of distribution. The “original rat,” as it is called, remains 
confined to Pulu tikus. MZws decumanus is most abundant on 
