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Show 1886.] MR. BOURNE ON THE FAUNA OF DIEGO GARCIA. 331 shed her spawn between her ventral fins, which were clasped tight together, and, when full, swam to the nest, and, turning on her back, deposited the spawn in it; this occurred several times, the male each time putting the spawn in its proper place and covering it with froth. As soon as the female had dropped all her spawn the male took entire possession of the nest and would not let his mate go anywhere near it, and treated her so badly that I had to place her in another tank to save her life. Unfortunately the spawn was not good, only a few eggs hatching, and the young fishes dying soon afterwards. " I have bred great quantities of the little Callichthys punctatus from the Amazons, but they never made the slightest attempt at making a nest, always depositing their spawn all over the tank, and even on the floating thermometer kept in it. "Yours faithfully, "J. A. M. VIPAN." The following papers were read :- 1. General Observations on the Fauna of Diego Garcia, Chagos Group. By GILBERT C. BOURNE, B.A., New College, Oxford. [Received May 15, 1886.] Diego Garcia is tbe southernmost atoll of the Chagos group in the Indian Ocean, lying in S. lat. 7° 13', and E. long. 72° 23'. It is of irregular shape, 13 miles long and 6 miles wide, consisting of a strip of land of an average breadth of a third of a mile, which nearly encircles the lagoon. The opening lies to the N.W., and is divided by three small islets into four channels, the largest of which is more than a mile wide, and deep enough to allow the largest ships to enter the lagoon. The formation is wholly of coral, and the land consists in different localities of sand, accumulated coral-boulders, and sand-rock or shingle-rock. It nowhere rises to a greater height than the waves have been able to accumulate fragments of coral, except in some places, where sand-dunes have been piled up by the wind to a height of 25 or 30 ft. above high-water level. As is usual in coral-formations, a reef some 60 yards broad encircles the shores ; this reef is nearly flat, is composed of a compact finely stratified coral-limestone, and is just left bare at the very lowest springtides. Growing coral is only found on the outer edge of the reef, but in some parts the Alcyonarian Helioporce and Tubiporce are found in large numbers on its surface. Many Holothurians, Echinids, Ophiurids, and Sponges are to be found on the flat surface of the reef between the tide-marks, and large Tridacnce are imbedded in it, showing the brilliant edges of their mantles above the rock. The naturalist who wades over the reef at low water will be abundantly rewarded in his search for Mollusca of all kinds, chiefly of the genera Cassis, Oliva, Turbo, Nerita, Aporrhais, Aplysia, and 22* |
