It is now very nearly fifty years since I published a revision of the genus Synthocus (Tr. S. Afr. Phil. Soc. XVIII, 1907, p. 89) which then contained only 18 species. Since that time five additional species have been described, namely S. tuberculatipennis and maculipes Hesse (Ann. S. Afr. Mus. XXV, 1929, pp. 504, 505) from South Africa; S. viduus Hustache (Rev. Zool. Bot. Afr. XXX, 1937, p- 182) from the Belgian Congo; S. singularis Hustache (Bull. Soc. Neuchät. 62, 1938, p. 71) from Angola; and S. nigeriensis Mshl. (Ann. Mag. N. H. [11] XII, 1945, p. 439). Another older species has also been added to the genus, because Dr. E. Haaf, who is now revising the vast genus Brachycerus, has made the interesting discovery that B. bottegi Gestro, from Somaliland, is not a Brachycerus but a true Synthocus. Thanks to information made available to me by Dr. Haaf I have been able to include the species in the accompanying key; but as the unique type is gummed on a card, it has been impossible to ascertain whether the median coxae are contiguous or otherwise. The species has therefore been included in both categories to facilitate identification.