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 bad 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 Callichthijs 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. 



[Eeceived May 15, 1886.] 



Diego Garcia is the 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 spring- 

 tides. Growing coral is only found on the outer edge of the reef, 

 but in some parts the Alcyonarian Heliopora and Tuhipora 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 abun- 

 dantly rewarded in his search for Mollusca of all kinds, chiefly of 

 the genera Cassis, Oliva, Turbo, Nerita, Aporrhais, Aplysia, and 



22* 



