The systematic position of the mongoose named by Gray Herpestes semitorquatus, and based on a specimen collected by Sir Hugh Low on the mainland of Borneo opposite Labuan Island, i. e. Brunei, has always been somewhat of a puzzle. Very few typical specimens are known and all of these come from the distributional area of Herpestes brachyurus. The type skull in the British Museum which I have examined, shows no relevant differences from skulls of H. brachyurus of comparable age. There is also no difference in proportions, the nakedness of the soles, nor in the hair structure between the two groups. The only difference that remains is that in colour. Herpestes-brachyurus is a very dark animal with a lot of black, whereas in H. semitorquatus the black pigment is greatly reduced, making the red ground colour predominant. The conclusion that I draw, is that the red and the blackish short-tailed mongooses are colour mutants of the same species, the oldest name of which is H. brachyurus Gray. This conclusion is emphasized by the fact that both the black and the red mutants vary geographically, and that the characters by which “Herpestes brachyurus sumatrius” Thomas from Sumatra differs from “H. b. rajah” Thomas from Borneo, are the same as those by which “Herpestes semitorquatus uniformis” Robinson and Kloss from Sumatra, differs from H. s. semitorquatus Gray from Borneo. In both cases the Sumatran animal is more uniform in colour, with a dark tail, whereas the Bornean animal is more finely speckled, and has a tail that is lighter than the body.