The metamorphic region of Madagascar has much in common with the “Mozam- bique Belt” of East and Central Africa, although the grade of metamorphism seen is often higher. No clear comparison can be drawn between the main subdivisions of the Madagascar Basement and those of the mainland; moreover, the unconformably overlying Crystalline Limestone Series has no known counterpart in Africa, while the major late Pre-Cambrian or Lower Palaeozoic sedimentary systems of the mainland, frequently but little altered or disturbed, are not represented in Madagascar, although there is a widespread Quartzite Series, ascribed to the Devono-Carboniferous, of somewhat different character. The principal metamorphism of the Basement rocks of Madagascar is ascribed to a major orogeny dated as 2600 m.y., but the older orogenies of the mainland, up to 3250 m.y., have not been recognized. The later Palaeozoic, Mesozoic and Tertiary sediments are in many respects closely comparable with those of the mainland, as may be expected from their position on opposite sides of a great geosyncline. While there are important differences in the associated older volcanic episodes, the Tertiary and post-Tertiary volcanism followed a similar course in both regions. Post-Tertiary rifting is present in Madagascar, but only locally and on a small scale. The geomorphological history of Madagascar compares closely with that of the mainland, the regions appearing to have responded similarly to the intermittent sinking of the intervening geosyncline. Intermittent uplift, with seaward tilting, has given rise to a step-like arrangement of erosion surfaces around a core of Basement highlands with maximum elevations ranging from 1000 to 2200 metres ; the ages of these surfaces, as determined mainly from their relations to fossiliferous sediments, range from Quaternary to the later Tertiary, mid-Tertiary, late Cretaceous and Jurassic.