star-fish, or sea-star, in zoology, a genus of insects of the order of vermes mollusca. It has a depressed body, covered with a coriaceous coat; is composed of five or more segments, running out from A central part, and furnished with numerous tentacula; and has the mouth in the centre.—The conformation of the mouth is this: The under part of each lobe runs towards a point with the rest at the centre of the body; and these several productions of the rays make a fort of lips, the ends of each of which are armed with a number of sharp teeth, which serve to take and convey the food into the body. From this mouth there goes a separate canal to all or many of the rays, which runs through their whole length, and becomes gradually narrower as it approaches the extremity. The tentacula resemble the horns of snails, but serve the animal to walk with. They are capable of being contracted or shortened; and it is only at the creature's moving that they are seen of their full length; at other times, no part of them is seen but the extremity of each, which is formed like a sort of button, being somewhat larger than the rest of the horn.
Most of the species of asterias are found in the British seas. 1. The glacialis, with five rays, depressed, broad at the base, yellow, and having a round striated operculum on the back, is the most common; it feeds on oysters, and is very destructive to the beds. 2. The clathra, or cancellate sea-star, with five short thick rays, hirsute beneath, cancellated above, is found with the former, but more rare. 3. The oculata, with five smooth rays, dotted or punctured, is of a fine purple colour, and is found about Anglesea. 4. The hispida, with five rays, broad, angulated at top, and rough with short bristles, is of a brown colour, and likewise found about Anglesea. 5. The placenta, with five very broad and membranaceous rays, extremely thin and flat, is found about Weymouth. 6. The sphaerulata, with a pentagonal indented body; a small globular bead between the base of each ray; the rays slender, jointed, taper, and hirsute on their sides; found off Anglesea. 7. The caput medusa, or arborecent sea-star, with five rays issuing from an angular body; the rays dividing into innumerable branches, growing slender as they recede from the base. These animals, in swimming, spreads like a net to their full length; and when he perceives any prey within them, draws them again, thus catching it with all the dexterity of a fisherman. It is an inhabitant of every sea; and is called by some the Magellanic star-fish and basket-fish. When it extends its rays fully, it forms a circle of near three feet in diameter. The fragments of these rays furnish the fossil entrochi. If we drown this animal in brandy or spirits of wine, and keep the rays flat and expanded in the execution, it is easy to extract by means of a pair of forceps the stomach of the animal whole and entire through the mouth. 8. The decacemos, has ten very slender rays, with numbers of long beards on the sides: the body is small, and surrounded beneath with ten small filiform rays. It inhabits the western coasts of Scotland.—There are several other species mentioned by authors; some of them of 10, 12, 13, or even 14 rays.
Aristotle and Pliny called this genus astre, and stella marina, from their resemblance to the pictured form of the stars of heaven; and they asserted that they were so exceedingly hot, as instantly to consume whatsoever they touched.
The fossil world has been greatly enriched by the fragments and remains of the several pieces of star-fish which have been converted into stones. See ASTERIA.
the ancient name of the bittern. See ARDEA.