At the heart of Africa lies a vast area, so remote, so inaccessible, and hence so little known, that for the explorer it possesses a fascination all its own. The interests of the geologist have perhaps received less recognition than those of his fellow-scientists from the pen of the traveller; and there must be much that he would wish to know lying hidden in these distant regions awaiting discovery and publication. There is thus an encouragement to make known any facts which may throw light upon the geological structure of those parts, however small the contribution may be.

While serving recently with the Anglo-French Boundary Commission (Niger-Chad) we found an outcrop of a fossil-bearing stratum in the region of the Sokoto, having, as shown in the accompanying map, giving its latitude and longitude, a position near the verge of the Great Sahara Desert. On my return, the specimens secured were submitted to the palæontologists of the British Museum, one of whom, Dr. F. A. Bather, has kindly drawn up the description which follows in a separate paper. For me it only remains to give a few particulars of the general and localized formation to supplement his account.

Generally, the country consists of sandy plains, roughly estimated as lying some 500 or 600 feet above sea-level. These plains are traversed by watercourses, which contain running water only for some five or six weeks in the year, the rainfall of 535 mm. lasting during three months. A permanent water-supply is obtained by deep wells, which in some places reach a depth of 400 feet before tapping a constant source.