Prof. H. Boschma, director of the Rijksmuseum van Natuurlijke Historie, sent me some Balanids associated with Millepora platyphylla Hemprich & Ehrenberg, partly preserved in formalin, partly in a dry state. The material was collected by the Snellius Expedition in 1930, the data concerning the present material are (Boschma, 1936, p. 19): "April 23-27. Obi latoe, northwest of Obi major (22). Most of the collecting was done on the reef of the small island Poeloe Toesa at the east side of Obi latoe. This is a highly varied reef with a great number of species of corals. A peculiar phenomenon observed here was the occurrence of multitudes of small brown flatworms on colonies of Merulina and Montipora, which covered the greater part of the surface of these corals. Among other groups of animals Balanids of large size attached to Millepora may be mentioned and several species of Foraminifera living on a sandy stretch with algae." In a letter dated August 24, 1949, Prof. Boschma wrote me in regard to the specimens dealt with here: "Part of the material is labelled "Poeloe Toesa", another part "Obi latoe". All this material was collected on the small island Pulu Tusa near the larger island Obi latu. The name of the Millepora is Millepora platyphylla Hemprich & Ehrenberg." The amended spelling of the localities is in conformity with modern practice. I want to thank Prof. Boschma for publishing the results of my investigations on these Balanids in the journal of the Leiden Museum. In the material I found two species of Balanids, viz.: i, Balanus tintinnabulum occator Darwin; 2, Pyrgoma milleporae Darwin, forma typica Darwin and forma snelliusi n. f.