While in all probability northern Venezuela has no rocks quite so ancient as those of Guayana, the geological history of this part of the country has been much more eventful, and the number of earthquakes suggest that even yet the form of the earth’s crust in this region is undergoing comparatively violent changes. As is commonly the case, to find the oldest rocks we have to search the hills, and because the masses of gneiss, silvery mica-schist, marble, and so on, which form the highest parts of much of the mountain region, were first studied by Mr. G. P. Wall in the Caribbean Hills in 1860, he named the whole the Caribbean Series. The beds which make up the series may have been deposited at a period corresponding to that of the ancient Silurian rocks of Wales, but it seems very possible that they are older in some parts than in others. They form the central region of the Venezuelan Andes, where there is a core of granite which probably cooled at a date subsequent to the consolidation of the gneiss and schists. The silvery mica-flakes of the latter are very often mistaken by the inhabitants for gold or silver ores, and the author had more than one pretty but valueless specimen offered for sale, with its locality to be revealed as a secret of great worth! The same rocks extend all the way along the coastal range across the Boca del Draco into Trinidad, and northward in Margarita the mountains are formed of similar gneisses and schists. In the Llanos north of El Baúl there is a peculiar elevated plateau known as La Galera, from which rise many hills of gneiss and granitic rock, but these may perhaps be an outlying island of the Guayana complex. After the deposits of the Caribbean Series had been consolidated and elevated into dry land, but before they had been thrown into high mountains such as they form to-day, perhaps at the same time that the granite of the Sierra Nevada of Mérida was being pushed up under them in a molten condition, the seas around were receiving deposits of quartz sand, mud, and lime, which were later consolidated to form a series of red and yellow sandstones, shales, slates, and black bituminous limestones, which now outcrop along the Sierras, and chiefly in the Segovia Highlands, suggesting for the whole the name Segovia Group. The animals which inhabited the seas of those times left their shells and remains in the rocks, and the forms (Ammonites, _Inoceramus_, &c.) which have been found by various travellers show that these deposits were formed at a period approximately corresponding to that of the lowest parts of our chalk or of the Cretaceous System generally.