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The bivalves recovered from the Holocene Bangkok Clay in the Lower Central Plain of Bangkok along with those obtained from modern shallow bottoms in Phetchaburi coastal area are recorded and described. The bivalve assemblages of the Holocene Bangkok Clay appear to parallel the Recent ones recovered at sea, from intertidal and shallow infralittoral, predominantly muddy, substrates. Arcoidea, Galeommatoidea, Tellinoidea and Veneroidea are the most diverse groups, often with species that occur abundantly. This paper covers 225 species, 35 out of them unidentified and, at least partly, previously undescribed. The species treated are complemented with taxonomic remarks when necessary and with information on respective ecological requirements if available. Except for a few species represented only by fragmented shells, all are illustrated. A list of references to the mollusk fauna of the Indo-Pacific Region is also given in order to provide facilities to the reader.

Faunal examination is made of 4 samples, 2 from the Recent Ban Laem Phak Bia sand spit, and 2 from the Holocene sand body of Ban Bang Ket. Fossil and modern assemblages are compared on the basis of overall composition, taxa abundances, and of autoecological investigation on life habit, substrate preference, feeding type, depth range and ecological meaning of the identified species. The Holocene assemblage of Ban Bang Ket, compared to the Recent one of Ban Laem Phak Bia, 1) exhibits generally similar overall composition and ecological structure, 2) contains much of the dominant species characterizing the modern assemblage, and 3) includes all taxa that are members of the living molluscan community. On this basis, the molluscan assemblage of Ban Bang Ket results to be the Holocene counterpart of the modern one of Ban Laem Phak Bia, and reflects the same environmental conditions recorded for the latter. Thus, the sand body near Ban Bang Ket is interpreted as a Holocene equivalent of the sand spit of Ban Laem Phak Bia., Sezione di Museologia Scientifica e Naturalistica, 2005: Volume Speciale

The scaphopods, gastropods and some newly found bivalves recovered from the Holocene Bangkok Clay in the Lower Central Plain of Bangkok along with those obtained from modern shallow bottoms in the Phetchaburi coastal area are recorded and described. The gastropod assemblages of the Holocene Bangkok Clay appear to parallel the Recent ones recovered at sea from intertidal and shallow infralittoral, predominantly muddy substrates. Rissoidea, Muricoidea, Conoidea and Pyramidelloidea are the most diverse groups, with species that often occur abundantly. This paper covers 336 species, of which 23 are proposed as new; 108 remain unidentified and are, at least partly, previously undescribed. The species treated are complemented with taxonomic remarks when necessary and with information on respective ecological requirements if available. Nearly all species are illustrated in the plates. A list of references to the mollusk fauna of the Indo-Pacific Region is also given.

The present paper examines Holocene and Recent molluscan associations (or assemblages) of Thailand and identifies pairs, each including a modern association and its fossil analog. The aim is to reconstruct precisely the environmental meaning of the Holocene associations, assuming that these have dwelled the same environment of their modern counterparts. The Anadara granosa-Cerithidea cingulata assemblage records innermost muddy tidal flat conditions, with mangrove vegetation. The Alveinus ojianus-Nuculana (Scaeoleda) mauritiana association thrived in an outer tidal flat, also muddy, that experienced sedimentary instability in turbid waters. The Nuculana (Jupiteria) puellata-Chrysallida melvilli association occurred in sandy mud, at the transition between intertidal and infralittoral zones, and denotes some scouring and turbulent water. The Timoclea (Chioneryx) scabra-Arcopagia pudica association dwelled upper infralittoral bottoms of sandy mud, hardly exceeding 10 m depth. Finally, based on the relative geographic position of the fossil Nuculana (Jupiteria) puellata-Chrysallida melvilli association and of its modern analog Nuculana (Jupiteria) puellata-Pitar (Costellipitar) manillae association, a progradation rate of the tidal flat of 1.6 m/yr during the last 820 years was calculated.