The area investigated is mainly a shallow shelf environment including the Gulf of Thailand and part of the South China Sea. Large amounts of precipitation and runoff cause marked seasonal variations in the temperatures and salinities of the sea water in the area. The Gulf sediments are dominated by olive brown muds, and the shelf sediments are dominated by yellow-brown sands.

The foraminiferal number, species number, and the percentage of planktonic Foraminifera increase with depth and distance off shore and toward mid-gulf.

Species of Globigerina constitute the eurythermal planktonic fauna and are relatively common in the

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inner shelf. Below 54 m. a diverse planktonic fauna, including the many warm water species, appears in the sediments.

Hyaline Foraminifera compose fifty per cent or more of the benthic population in all but the two stations which are located near large rivers.

The beach fauna is dominated by Ammonia beccarii sobrina and various species of Elphidium. The inner shelf fauna has an abundance of various Ammonia species, Hanzawaia nipponica, and Rotorbinella versiformis. The outer shelf fauna consists largely of Bolivina robusta, Cibicides haidingeri pacificus, and Epistominella pulchra. The dominant upper bathyal species are Cassidulina subglobosa, Cibicides pseudoungerianus, and Gumbelitria vivans.

Size measurements of a few species indicated a tendency toward dwarfism in the fauna of the closed basin in the Gulf.

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