In 1903 (in vol. lix of this Journal) I described the occurrence in Southern Rhodesia of deposits of Permo-Carboniferous age that have since been correlated with the Karroo System of South Africa. In the present communication will be traced their extension into Northern Rhodesia. There they are found occupying the lowlands of the Zambesi basin, and they also constitute the floors of the trench-like valleys of the Lusenfwa River (or Luano plains), of the Lukasashi River, and probably of the Luangwa. These depressions form a more or less continuous succession of troughs bisecting Rhodesia diagonally, along a distance of some 800 miles, that is, from the Deka River to the head of the Luangwa. They lie some 2000 feet below the surrounding country, which is of plateau type and is made up of metamorphic and crystalline rocks of the pre-Karroo complex. The change from upland to valleyplains is generally abrupt, giving rise to steep escarpments that appear as mountains when viewed from the lower position. Nowhere, so far, in the vicinity of these depressions have ‘highlevel’ areas of Karroo rocks been met with on the plateau, and one's first impression is that these basins are vestiges or' an original landscape, in which the sediments were deposited. But we have been prepared by :Mr. G. W. Lamplugh, in his description of the Deka Fault, for great displacements of Karroo strata and earthmovements, and there is ample evidence to show that these valleys and low-lying regions of sediments are largely due to