During the carrying out of field work in connection with the investigation of plague in the Union of South Africa, certain fleas which appeared to be new were taken in the nests of water rats and on a golden rock mouse in the Karroo.

Whilst resembling Chiastopsylla, Rosthsch., morphologically, the fleas from the Karroo rats differ from that genus in the absence of tooth-like spines at the genal margin of the head, and the flea taken on the rock mouse differs in possessing no pronotal comb, in addition to the absence of spines at the genal margin of the head. It was thought that these differences would require the erection of new genera for the reception of these fleas ; two specimens, however, of one of the species showed an incomplete set of genal spines, and Dr. Jordan, who kindly examined the material, considers that all the fleas described below belong to the genus Chiastopsylla. Apparently, if one may judge from the presence of genal spines in the two specimens found, certain species of this genus have been recently evolved.