1. Velain, C., Bull. Geol. Soc. France, 7, 278 (1879).
2. Bauer, M., Neues Jahrb. Min., 2, 163 (1898).
3. Baker, B. H., Mem. 3, Geol. Surv. Kenya (in the press).
4. Miller, J. A., and Mudie, J. D., Nature, 192, 1174 (1961).
5. Loncarevic, B. D., and Mathews, D. H., New Sci., 14, 513 (1962).