332 MR. BOURNE ON THE FAUNA OF DIEGO GARCIA. [Juiie 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 oi'ten 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- 

 l)oulders, 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 " (Sceevola 

 kcenigii), "Veloute" {Tourneforiia argentea), and " Bois de feu" 

 {Guettarda speciosci) 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-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 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 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 oft' to continents and larger islands for the remainder of the year. 



