332 MR. BOURNE ON THE FAUNA OF DIEGO GARCIA. [June 29, 
Peronia; and, by searching among the holes in the reef-rock, tolerably 
large specimens of Octopus may be found. Small Scaroids and File- 
fishes of great beauty swim rapidly away from the approach of the 
observer, and Murznoids of various sizes, chiefly of the genus 
Ophichthys, are to be found lurking under the scattered boulders of 
the reef. A small species of Periophthalmus is very abundant, but is 
very difficult to capture, even in the pools which have been left by 
the retreating tide, for it escapes by leaping from pool to pool with 
great agility. This species of Periophthalmus appears to differ in 
habit from the Pacific species, in that its paired fins are not so well 
adapted for progression on land; it leaves the water but rarely, and 
is unable to sustain life in the air for a longer period than half an 
hour. The boulders at the edge of the sea are occupied by swarms 
of crabs of the genus Grapsus ; and the strip of dazzling white sand 
that borders the shore is often covered with small white or grey 
crabs of the genus Ocypus. 
The outer edge of the land is always composed of a heap of coral- 
boulders, many of them of considerable size, which have been heaped 
up by the waves. This heap of boulders forms a sort of rampart all 
round the outer edge of the island, which slopes down to the lower- 
lying land, raised only two or three feet above the level of the lagoon 
at high tide. The whole island is densely covered with vegetation, 
the bushes known by the native names of ‘‘ Manioc”’ (Scevola 
kenigit), “ Velouté” (Tourneforlia argentea), and “ Bois de feu” 
(Guettarda speciosa) forming impenetrable thickets near the shores. 
The central and interior parts of the strip of land are covered with 
cocoa-nut palms, beneath which, from the continual decay of the 
fallen leaves, a rich peaty mould has become established. The im- 
ported animals of the island are donkeys, hogs, fowls, and rats; the 
last-uamed swarm on the main island and do great destruction 
among the cocoa-nuts, but, curiously enough, they have not yet 
found their way to the islets in the mouth of the lagoon. Cattle 
do not thrive, but sheep have been imported and appear to do well 
on the herbage which covers the more open spaces ; the first con- 
signment was unfortunately destroyed by the donkeys, to whom 
sheep were utter strangers. 
When I arrived at Diego Garcia on September 15th, 1885, Terns 
were breeding in countless numbers on some of the less frequented 
parts of the island. The dark grey Terns build rough nests, com- 
posed of a heap of sticks and leaves piled up in the forks of trees and 
bushes ; in each of these a single egg is laid, on which the female sits. 
The black-and-white Terns lay a single egg on the bare ground, which 
is apparently hatched by the heat of the sun, for I never saw one of 
these birds sitting. But it was difficult to make observations, for the 
negroes soon took all the eggs, and wantonly destroyed hundreds 
of the birds, which couid easily be knocked down with a stick as 
they flew screaming round one’s head. As soon as the breeding- 
season was over, the number of Terns diminished very considerably ; 
it seems that they assemble in these remote islands for breeding, and 
fly off to continents and larger islands for the remainder of the year. 
