BRITTLE STAR, also called SNAKE STAR, and SAND STAR, a member of the order of Ophiuroidea, class Asteroidea, of the phylum Echinodermata (q.v.), a class of star fish-like echinoderms. It is characterized by the body forming a flattened disc, with cylin drical arms, the stomach not extending into the arms, and there is no intestine or anal opening. The ambulacral furrow is covered by the ventral shields of the tegument, so that the ambulacral feet project from the sides of the arm. It moves faster than the true star fish, the arms being more slender and flexible and more easily broken. An ophiuran which has accidentally lost an arm can reproduce it by budding. In species of Ophiothela and Ophiactis the body divides in two spontane ously, having three arms on one side and two on the other, while the disc looks as if it had been cut in two by a knife, and three new arms had then grown out from the cut side.
Few specimens reach a size in excess of an inch in diameter and the rays seldom exceed 10 inches in length. The ophiurans in most cases undergo a decided metamorphosis like that of the starfish. The larva, called a •Pluteus,'' is free-swimming, though in some species the young, in a modified larval condi uon, reside in a pouch situated above the mouth of the parent, finally escaping and swimming freely about. Our most .common
brittle star is Ophiopholis aculeata, which may be found at low-water mark, and especially among the roots of Laminana thrown upon the beach. They have little means of defense, and so live under rocks or buried in mud and sand. They are nearly all vegetable feeders though possibly some are carnivorous. It is variable in color, but beautifully spotted with pale and brown, its general hue being a brick red. Ophiurans are widely distributed, and live at depths between low-water mark and 2,000 fathoms. Fossil ophiurans do not occur in formations older than the Upper Silurian, where they are represented by the genera Pro taster, Palcrodiscus, Acroura and Eucaladia; generic forms closely like those now living appear in the mushcelkalk beds of Europe (Middle Trias). There are about 600 known species, of which few belong to the shore waters of the United States.