Page:South African Geology - Schwarz - 1912.djvu/156

 but Lepidodendron does occur, as well as the roots of this forest tree, Stigmaria. These forms probably originated in the Southern Hemisphere, and were driven northwards on the advancing cold of the succeeding glacial epoch. When they reached the equator they were again driven north by the recurrence of genial climate, and the heat of the tropics became too much for them. A few stragglers came south again, and are found in the Karroo sediments. The Spirophyton is a screwlike seaweed with a very wide flange marked with sickle-shaped ribs. It occurs in Devonian and Carboniferous rocks in Europe and America. There is another species in which the flange of the screw is broken up into a number of rods which radiate screw fashion from a central axis. The root of the South African Spirophyton is always downwards; in other countries the seaweed apparently grew downward. Hastimima is a gigantic water scorpion (Eurypterid).

These three series — the Table Mountain, Bokkeveld, and Witteberg — form a fairly compact formation, the Cape Formation. At the bottom is a more or less pure quartz series, then a deep-water series, and finally a ferruginous sandstone and shale series. This threefold formation is simply a repetition of what occurred farther north in previous times, when the quartzites of the Black Reef Series were followed by the dolomite, which in turn was followed by the Pretoria Series. The conditions of the deposition of the Cape Formation can be fairly well established. The land lay to the north, the shore line in the beginning running east and west a little south of Kimberley. There was probably a southern shore line formed by the prolongation of the Madagascar ridge, and in the strait thus formed the Table Mountain