The feet move independently, and the starfish walks much faster than would be imagined. This can be illustrated by the sudden appearance of the starfish, in Long Island Sound. One night when the oyster men left the beds no starfishes were seen. The following day they were there in such vast quantities that it was estimated they covered the entire bed, two or three deep, and tens of thousands of dollars were lost by the destruction of the oysters. How an oyster can be opened by a soft, helpless starfish would seem a mystery; but it is a very easy matter. The starfish drags itself over the shell and places its mouth at the end, extending its long arms downward, literally swallowing part of the shell. It is supposed to eject some secretion into the shell that causes it to open. VIII. OCEAN HEDGEHOGS (_The Echini_) [Illustration: FIG. 51.--Sea urchins burrowing in the rocks.] On the Florida Reef and off the rocky shores of California one of the most conspicuous among the rock-living animals is the black, long-spined Echinus. In the water it looks like a huge pincushion (Fig. 51) filled with black pins, points outward, and every crack and crevice is filled with them. When found on the beach, despoiled of their spines, they resemble bleached shells, and are then known in Florida as sea eggs (Fig. 52). The long black spines are continually moving up and down, and constitute the armament of the sea urchin, and an effective one to all except very large fishes, as some rays, which have pavementlike teeth fitted particularly for such not especially dainty morsels. The spines emit a bluish secretion which is left in the wounds made by them, and is more or less poisonous. This common sea urchin is a type of hundreds found in almost all seas from very shallow water to the abysmal regions of the ocean. [Illustration: FIG. 52.--Sea urchin without its spines.] [Illustration: FIG. 53.--Short-spined sea urchin, showing the biting teeth.] Some sea urchins have short spines (Fig. 53) and are almost pure white; some are flat like the sand dollars, the spines feeling like sandpaper, so short and fine are they. The latter are small, and appear to be covered with waving filaments. Many have spines like needles; in others the latter are blunt, clublike organs. Many other strange variations are seen in an exhibition of the various kinds in some museums. None are more remarkable than those having five holes through them like Chinese money (Fig. 54). [Illustration: FIG. 54.--Flat sea urchin, "sand dollar."]