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Show 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 Mursenoids 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" (Scaivota kcenigii), "Veloute" (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 imported animals of the island are donkeys, hogs, fowls, and rats; the last-named 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 consignment 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, composed 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 could 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. |