GENERAL REPORT ON THE MATERIALS SENT FROM FUNAFUTI 177 



and form shoals, often with only a few feet of water upon them at high tide, the 

 whole of the bottom of the Funafuti Lagoon is covered with a dense growth of the 

 green calcareous alga Halimeda opuntia Lam., a well-known member of the order 

 Siphonese, group Chlorophyceae. This growth of Halimeda appears to be most 

 vigorous in the shallower parts of the lagoon, but everywhere it forms a green living 

 carpet down to depths of 120 feet, and is occasionally found alive at greater depths. 

 The Halimeda fronds are often more or less covered with attached organisms, such 

 as the foraminifera Sagenina, Polytrema, &c., with Sjnrorhis, SerpulcB, Polyzoa, &c., 

 and other organisms. Intermingled with the living Halimeda and its broken and 

 dead remains are found numerous foraminifera, with Ostracoda and alcyonarian and 

 tunicate spicules, as well as remains of Pteropoda, Gastropoda, Pelecypoda, Crustacea 

 and other forms of animal life, with several forms of LitJiotJiam'nion. In the central and 

 deeper parts of the lagoon the number of foraminifera is comparatively small, seldom 

 exceeding 10 per cent, of the whole mass, and consisting only of species adherent to 

 the fronds of Halimeda, with the free forms Amphistegina and Heterostegina. But 

 in the shallower water on the edges of the lagoon, the foraminifera and other 

 organisms increase in number till they constitute the bulk of the materials of the 

 sandy bottom. As shown by Mr. Chapman, the forms of foraminifera are more 

 numerous and varied at the Fuafatu end of the line of soundings, where the lagoon 

 is open to the ocean, than at the more enclosed end at Fongafale.* 



The genera of foraminifera which abound in the shallow water are the same as 

 those found on the lagoon beaches, and include the conspicuous spurred forms 

 Calcarina and Tinoporus, with many species of Miliolina, while the different varieties 

 of Orhitolites, Globigerina and other pelagic forms occur much more rarely, and 

 usually as dwarfed specimens ; these were probably washed in from the ocean 

 outside. On the lagoon shore at Fongafale, twenty-one species of foraminifera are 

 recorded by Mr. Chapman as occurring, while at the Fuafatu shore of the lagoon the 

 number is twenty-eight, the increase being accounted for by the greater increase 

 of marine conditions, due to wide openings in the atoll-rim and the richer supply 

 of food. The effect of advantageous conditions is shown by increase in the size of 

 individuals as well as by the number and diversity of species. 



The proportions of the several kinds of organisms in the eighteen samples dredged 

 in the lagoon, at distances of half a mile from Fongafale to Fuafatu, were determined 

 by taking weighed portions and picking out the various organisms. The results 

 obtained were as follows : — 



* F. Chapman, " Foraminifera from the Lagoon of Funafuti," ' Linn. Soc. Journ.' (Zoology), vol. 28 

 (1901-03), pp. 161-210. 



2 A 



