I. General Description of the Area. Beyond the coastal and volcanic belts of Mozambique—already described in a previous contribution 1 —the country assumes the form of a gently undulating plateau that gradually rises towards the west. As one proceeds inland its surface becomes increasingly diversified by inselberge and clusters of abrupt hills until, west of Ribawe, where the plateau reaches an elevation of nearly 2000 feet, the scenery becomes more typically of a highland character and the stretches of unbroken plateau less extensive. Throughout the whole area traversed by the staff of the Memba Minerals Ltd. (after the Cretaceous and Tertiary formations had been left behind) no rocks were found that were not of igneous or metamorphic origin, or that, like laterite, 1 could not be traced immediately back to an igneous or metamorphic parent-rock or to solutions percolating through such rocks. (See index-map, fig. 1, p. 32.) The dominant rock of the country, persistent to a degree that often becomes monotonous, is a grey biotite-gneiss. Interfoliated with the gneiss are occasional lenticular masses of hornblende-gneiss and amphibolite, and with these, smaller bands and lenticles of crystalline limestone are sometimes intimately associated. Elsewhere the gneisses become coarse and garnetiferous, and in some places eclogites and basic granulites occur. Schists were found very sparingly, and the known exposures are limited to three areas: the north-east of the territory behind the broadened coastal plain in the neighbourhood of the mouth of the Lurio, the district around Memba, and the central coastal region between the Mitikiti