The fossil remains of rodents described in the present paper are from various localities. The large extinct musk rat Megalomys occurs in reddish-brown phosphatic “oolite” fillings of irregular cavities in a marine limestone found by Mr. P. H. DE BUISONJÉ in the north-western part of the Duivelsklip, eastern Curaçao, about 50 m above sea-level. The “oolite” also contains scanty remains of lizards, snakes, and of a bat. Fragmentary molluscs present possibly include Cerion uva (L.), a recent, very common, terrestrial species, as well as other gastropods, many opercula of which were found. Samples of a phosphatic “oölite” deposit collected in 1937 by Dr. P. WAGENAAR HUMMELINCK from an escarpment near Fontein, Bonaire, proved to contain jaws, with teeth, of a genus of hesperomyine rodents, Thomasomys a single snake vertebra; and mollusc remains including what seem to be their coprolites.