The carcinological collection of our Museum contains no less than 270 specimens of the genus Matuta Fabr., preserved in spirits, collected in the seas of the Indo-Pacific Region, from the shores of the Red Sea to those of the eastern islands of the Malayan Archipelago. They belong to six different species, among which the very common Matuta victrix Fabr. is represented by no less than nearly 200 specimens, the very rare Matuta granulosa Miers on the contrary only by one single individual. Mr. Miers in his excellent Monograph of this genus distinguished nine species and afterwards described a tenth, the Matuta circulifera Miers. Of these forms the Matuta laevidactyla Miers is not represented in our collection, while the Matuta lineifera Miers, Matuta circulifera Miers and Matuta obtusifrons Miers must be united, the former two with the Matuta lunaris Herbst ( rubrolineata Miers), the third with the Matuta picta Hess (Miers), as remarkable varieties of these species. As characters of first importance in the definition of the species must be considered: the course of the ridge on the outer surface of the hands of the male; the presence and shape of the spines or tubercles with which the latter is armed, and the ridge on the mobile finger being beaded over its whole length or not. I regard as characters of second importance the greater or lesser development of the tubercules on the surface and on the lateral margins of the carapace, and the more or less distinct granulation of the latter and of the outer surface of the hands, while the manner of coloration of the cephalothorax must be considered as a character of a very slight value.