OCR Text |
Show 1 9 0 5 .] CAPE VERDE MARINE FAUNA. 183 but in one part a larger channel exists on its land side. In this a constant current is produced by the flowing away of the spray thrown over the reef-edge to the northerly opening of the channel. Obviously this current is the means by which the channel was produced. Landwards is a sand-beach, and in places a small amount of very soft beacli-sandstone, at a level of about three feet vertically above the reef-flat. Text-fig. 26. The edge is irregular, consisting of a line of rock-masses of nearly equal height, i. e. a few inches higher than the general level, and usually perfectly continuous with the reef-flat, and its surface is completely covered with nullipore giving a characteristic irregularity. There is a precipitous drop into one or two fathoms of water, beyond which is a slope of sand and stones. In short, all appearances are those of a growing nullipore-reef with beach-sandstone towards its landward side, but examination shows that sandstone extends to the seaward edge, being merely plastered |