sometimes so abundant that it gives a rosy hue to considerable areas of the sea. It attains a length of three or four inches, and in form is not very unlike an elongated melon with one end cut square off.
Closely related to idyia is pleurobrachia, one of the commonest of the "comb-bearers," or Ctenophoræ, on the northern coast of the United States. This jelly-fish, less than an inch in length, like all other Ctenophoræ, has eight rows of locomotive fringes dividing the surface of the body into regions as the ribs divide the surface of a musk-melon. Besides these eight rows of fringes, or locomotive organs, it has two most extraordinary tentacles; and no form of expansion, or contraction, or curve, or spiral, can be conceived of, which these wonderfully constructed tentacles do not assume as this transparent jelly-fish moves freely through the water.
If the visitor to the sea-shore will go down among the big rocks left bare by the retiring tide, and will lift up the long sea-weeds which hang from their sides, he will find the curious "starfishes," or "sea-stars," in some cases in great profusion, and clinging to the surface of the rock so firmly that they often leave some of their locomotive suckers attached when too quickly lifted from their places.
The starfishes have the body so gradually merging into the arms
Fig. 22.—Starfish (Asteracanthion).
or rays that one can hardly tell where the body ends and the arms begin; and this enables one to readily distinguish them at sight from the "serpent-stars," which are sometimes called star-fishes, and of
