Material and data collected by the British Museum (Natural History) South West Africa Expedition (1949-1950) throw new light on the taxonomy of the Karroo and Red-back Larks, usually assigned to the genera Calendulauda and Pseudammomanes. Birds of two different colours, apparently identical in every other respect, were found in each other's company near the mouth of the Orange River. The 'grey' birds were thought to be Calendulauda albescens and the 'red' birds Pseudammomanes ( ? species). It now seems that these birds belong to two groups which may be more closely related than has been recognized hitherto. The purpose of this paper is to examine this matter in the light of the data now available.