ASTE'RIAS (Lam.), a genus of Radiated Animals widely diffused over the seas. The Linniean genus comprises every form of radiation which appears in the tribe, but the genus Asterias of Lamarck includes only the Star-Fishes properly so called. These are divided into two sections, 'the Scutellated Star-Fishes,' and 'the Radiated Star Fishes: The former have an angular body, the lobes or rays of which are short, their length not exceeding the diameter of the disk : the latter have a body furnished with elongated rays, whose length far exceeds the diameter of the disk. The following is a general description of the animals to which the name Asteriaz has been applied : Each ray is furnished with a longitudinal furrow on its lower side, and this furrow is pierced laterally with amall.holes, through which pass the feet or tentacula, which are membranous, cylindrical, and each of them terminated with a little disk, which performs the office of a cupping-glass, somewhat in the same manner as the acetabula or suckers of the cuttlefishes. By elongating or shortening these
numerous little organs, and by fixing them by means of their tern:ilia' disks, the progressive motions of the Star-Fish are regulated. The rest of the lower surface is furnished with small moveable spines, which also assist progression. The whole surface is also pierced by pores, through which pass tubes much smaller than the feet, serving probably to absorb the water, and to introduce it into the general cavity, for the purposes of a kind of respiration. A large stomach lies close to the mouth; and two ramified ceeca, each suspended to a kind of mesentery, are given off to each ray, which is also furnished with two ovaries, by means of which the animals are supposed to reproduce their species without the aid of a second individual. A fine cord, which surrounds the mouth and sends a branch to each SIM, is considered as the development of their nervous system. [Asrensan.s:; . ECIIINODERMATA.]