FAUNA OF THE MONTE BELLO ISLANDS. 629 
supply. After the rains, water may be obtained from surface- 
diggings in the sand-hills situated to the west side of the island. 
Trimouille in many respects differs markedly from Hermite 
Island. The coast-line is far more regular, and there is but one 
inlet. This is quite unlike the lagoons of Hermite, for there are 
no rocky margins, and the dunes rise directly from shores of 
white sand. It forms, in fact, a more or less circular bay, with 
a narrow entrance. From the south side there runs off a tidal 
creek, around which there is a considerable growth of mangrove, 
but the Avicennia and Brugwera are intermixed, and do not 
form separate zones. The vegetation here is also peculiar, con- 
sisting almost entirely of Chenopodiaceous plants comprising 
both shr ubs and herbs, mostly of the genus Atriplex, A. isatidea 
Mog. covering large areas of the sandy foreshore. 
This particular spot is the chief haunt of a small bird, Zon- 
eginthus castanotis roebucki, which though widely distributed on 
the mainland, is in the Monte Bello Group confined to Trimouille, 
though individuals occasionally cross over to South-East Island, 
which lies off its south-eastern end. (See p. 636.) 
Nearly the whole of Trimouille is covered with blown sand, 
which towards the north-western end has collected into dunes 
of considerable size, two of which are particularly prominent, 
the largest rising to a height of 120 feet. At the foot of this 
hill, fresh water can be permanently obtained by shallow digging. 
The sand at the south-eastern extremity of the island is very 
coarse in texture, almost gravel, becoming gradually finer 
towards the north-western end. This sifting effect, due to the 
wind, was possibly of only a temporary nature, the result of a 
recent gale. 
As might be anticipated, the vegetation is far less luxuriant 
and more scattered than on Hermite Island, though it is quite as 
varied. Spinifex is much in evidence, and on the sand-hills 
facing the sea one frequently meets with the widely-distributed 
Tpomeca pes-capre, growing in a form with immensely long 
trailing stems, with erect tufts of glossy green leaves and pink 
flowers, separated by internodes as much as 20 feet in length. 
Ls ribulus cistoides Linn., Boerhaavia diffusa Linn., and B. mesic 
are all common, the latter often trailing up over the shrubs like 
a regular climber, though it grows equally well alone. 
Of the smaller islands little need be said, for they embody to 
a greater or lesser extent characteristics already deseribed. There 
is quite a varied flora on some of the smallest outlying islets, for 
the soil has an extra fertility imparted to it by the *mutton- 
birds,’ which breed in large numbers in burrows in the sand and 
holes in the rocks. 
In the following survey of the animals represented, stress has 
been laid upon small differences which may indicate zoological 
isolation, and trinomials have been adopted wherever it was 
thought desirable, but only where the series show uniformity. 
