BRITTLE STARS (so called from being brittle or fragile). A class of starfish-like echinoderms, technically known as Ophiuroidea, excluding the basket-fish. The brittle stars are a widely distributed group of animals, like all the echinoderms, exclusively marine; found in all seas, but most abundant in the tropics, and espe cially in the West Indian region. They are common at all depths, but are especially abun dant in comparatively shallow water. None of them reach a very large size, few having the body or disk more than an inch in diameter, and the arms or rays are rarely ten inches in length. In color there is 'the most extraordinary vari ety. While some are black, brown, dull olive, or even pure white, others are of the most gor geous shades of green, blue, red, and yellow, or exhibit the most beautiful combinations of hues. In some the disk is smooth and the arms terete, with very short, flat, and appressed a•m-spines; in others, the whole disk is covered with spines, sometimes short and opaque, but often long, slender, and glassy, and the flattened arms bear very long and beautifully transparent arm spines. In fact, the variety in the shape and covering of the disk and arms is quite as great as is that in color. The arms, though flexible
from side to side, are very slightly flexible up and down. and are therefore very easily broken. It is from this circumstance that the name brittle star has arisen. They are usually rather slow-moving animals, with little power of escap ing from their enemies, and with no means of de fense save such as the spines afford. Accord ingly, they live under rocks or buried in mud or sand, where there is little danger of their being seen. A few species, however, show con siderable agility in escaping from an enemy, and run about rapidly from rock to rock as they are pursued. They are practically all vegetable feeders or scavengers, though possibly some are carnivorous. About 600 species of. brittle stars are known, of which only a few arc found along the shores of the States. About half a dozen forms occur in shallow' water along shore, north of ('ape Hatteras, but south of that point they become very abundant. The Pacific Coast forms are at preselat very slightly known.