In the latter half of 1911, I had the opportunity of examining a group of crystalline rocks situated immediately below the southern edge of the great lava-plateau of the Kapiti Plains, and embracing many varieties of reconstructed sediments, from quartz-schists to highly crystalline marbles. Scattered outcrops of similar rocks have been described by Mr. Maufe from other localities in the Protectorate. The rocks here described were found in approximately lat. 2° S. and long. 37° E., and, so far as I was able to follow them, form the ground drained by the headwaters of the Turoka River, a designation which I think might well be applied to the group, as the name is one of the few found on the usual maps-of the district, and is likely in the future to become more widely known as an important station on the Magadi Branch Railway. The section to which I desire to draw attention is found on the right bank of a stream immediately south of the old ‘safari’ route to the Lake, about a couple of miles above the site of Turoka Station. In apparent ascending order, the following rocks are met with:— (1) At the base, a hornblende-schist, of which about 3 feet 5 inches is visible. A thin section of this rock shows large irregular plates of the common green hornblende, contained in a rather granular mosaic of water-clear plagioclase and quartz. The felspar is often untwinned, and commonly exhibits graduated zoning. In one part of the slide