Abstract
Survey work on the American Samoan island of Olosega, one of the three Manu'a Islands (Ta'(u) over bar, Ofu, Olosega), increased the known land snail fauna of the island from 6 to 30 species. Of these species, 17 are native to the islands and 13 are introduced. Most notable was the discovery of Samoana thurstoni (Cooke and Crampton, 1930) (Partulidae), previously considered an Ofu endemic. The entire land snail fauna of Mann a is composed of 45 species, with 40 on Ta'(u) over bar, 32 on Ofu, and 30 on Olosega. The three islands have 23 species in common. Endemism is low. Each island appears to have a random subset of the total species, though this may partly reflect a need for further survey work as well as true randomness in the natural construction of the faunas. While some native species seem to be extinct, others are surviving. However, the faunas of all three islands, especially the ground-level faunas, are dominated by alien species, notably species of Subulinidae. That such a relatively accessible island as Olosega should yield so many new records suggests that additional survey work is necessary throughout much of the Pacific before we can have the baseline inventory of Pacific land snail biodiversity necessary for its conservation.