Abstract
1. The present paper deals with the carcinological fauna of the Izu-Ohshima and adjacent islands (shown in text-figures 1〜2) during the years 1954〜1965. 2. The specimens of crabs hitherto idetified number 130 species referable to 78 genera and 16 families as shown in table 1. Biogeographycally, the authors divided these specieis into 7 routes, after the view of Sakai (1940, 1. C.). [table] 3. The new northern limit of the tropical species number 22, including three noteworthy species, which have hitherto been recorded from distant southern localities such as Bonin Island, Northern Daitojima and Loo Choo. 4. The features of the fauna of these islands generally resembling those of the southern Japan; some species to have extended from the Hachijo Island, but the most show more tropical or subtropical aspects than in the adjacent districts of the Japanese mainlands. 5. Izu-Ohshima is a volcanic island and is surrounded by rock beaches but we could obtain 3 species of the sand crab--Ocypoda stimpsoni, O. cordimana and Scopimera globosa; no typical esturine areas, but could obtain Eriocheir japonicus and Sesarma (Holometopus) haematocheir; and only a few fresh water streams but Potamon (Geothelphusa) dehaani is not uncommon. 6. Seven species enumerated below are rare in Japanese carcinological fauna, -Lasiodromia coppingeri unidentata, Achaeopsis rostrata, Platymaja myville-thomsoni, Ovalipes iridescens, Charybdis orientaris, Lybia tessellata and Geograpsus crinipes.
