A Revision of the Australian Pearl-shells, Genus Pinctada (Lamelli-branchia)

Characters used in the taxonomy of pearl-shells are reviewed and their variation with age and environment is discussed. Extensive variations with age are revealed. The growth processes have proved to be the most distinctive and invariable criterion of species but are highly susceptible to erosion and mechanical damage. Other characters of major importance are the hinge teeth, general outline of shell, convexity, external markings, and internal shell margin. The soft parts are of little value in delineating species. Phylogenetic relationships within the genus are considered. It is held that the lingah type of pearl oyster is the most primitive. A key to the Australian species is given. On the basis of the review of taxonomic characters, 31 trivial names occurring in a check-list of Australian species are rearranged under six specific headings. These synonymies are discussed, the species redescribed, and the geographical ranges reviewed.