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This paper is a somewhat revised and updated version of a report, written in 1973 after our 9-day visit, at the request of Mr. Marlon Brando, proprietor of Tetiaroa Atoll, and published here with his accord. The original version was based on that visit to the atoll, as explained in the introduction. It was supplemented by a few observations called from herbarium specimens and field notes of Dr. Gerrit Wilder, who visited the island briefly on March 12, 1925 and August 30, 1929, and of E. H. Quayle, of the Whitney Expedition, who stopped there on November 19-21, 1921.

As of 1969, the scientific community had no general information on the natural history of Namoluk Atoll in the Eastern Caroline Islands of Micronesia. The only significant published source for the atoll was an ethnographic and linguistic account provided by the German physician. Max Girschner (1912, 1913), that contained a few brief passages on the biology and physical environment of the atoll. With this lack of basic descriptive environmental information in mind, I resolved to make observations and collections of specimens of use to other atoll scholars ancillary to an anthropological research project which I undertook on Namoluk from 1969-1971.

Rarotonga and Aitutaki form the summits of separate volcanic masses rising from depths of 4000 m, at which depth the cones are 45-55 km in diameter (Summerhayes and Kibblewh 1966, 1967).The lower slopes of the cones average 15-25 increasing to 30 in the upper 750 m and becoming very steep the surface reef is approached. The Mauke-Aitutaki line of islands is thought to be of early Tertiary age: the surface volcanics are much eroded, with a subdued topography, or are capped with limestones (Wood, 1967; Wood and Hay, 1970). On Rarotonga, where the relief is much stronger (maximum altitude 640 m), radiometric ages of 2.3-2.8 million years date the 1 as Pliocene (Tarling, 1967). Mangaia, with a cap of Oligoce Miocene limestones, must be much older (Marshall, 1927). Evi dence from the deep-sea drilling programme indicates that th ocean floor in the area of the southern Cooks is Paleogene (22.5-65 million years) in age (Winterer, 1973), thus provid a maximum age for the islands. It is probable that the gross history of the Cooks resembles that of other, better-known reef-capped Pacific volcanic cones known to have been initia in the early Tertiary.

Satawal is a small flat coral island in the west central Caroline Islands about 1050 km east-south-east of Yap Island, at latitude 7'21' N, longitude 147'02' E. Although its surface is locally somewhat irregular, its greatest height is not more than about 4 meters above mean low water. Its long axis is about east-west and its area is 1.3 square km. It is surrounded by a fringing reef upward of 100 meters wide. It has no lagoon, so would be classified according to Tayama's scheme as a table reef. From the viewpoint of land ecology it is an atoll. The substratum varies from sandy to boulders, with some peat very locally. The beaches are sandy around the western half, of pebbles and cobbles around the eastern half.

Fais (Tromelin) is an elevated coral island, surrounded by interrupted cliffs 15-20 meters high, lying some 140 miles east of Yap Island, at latitude 9'46' N, longitude 140'31' E in the western Caroline Islands. It has an area of 2.8 square km, and has a population of about 300 people, Micronesians, speaking a dialect of the Ulithi-Woleai tongue. As with many such raised coral islands, valuable calcium phosphate deposits occur on Fais, the greater portion of which was removed and exported during the period of Japanese rule (1914-1945).