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One of the Echinodermata.

Relating or belonging to the echinoderms.

he animal kingdom. By many writers it was formerly included in the Radiata. [Written also Echinoderma.]

Relating to Echinodermata; echinodermal.

ing to ambulacra; avenuelike; as, the ambulacral ossicles, plates, spines, and suckers of echinoderms.

One of the radical zones of echinoderms, along which run the principal nerves, blood vessels, and water tubes. These zones usually bear rows of locomotive suckers or tentacles, which protrude from regular pores. In star fishes they occupy the grooves along the under side of the rays.

ncluding the annelids and allied groups; sometimes made to include also the helminths and echinoderms. [Written also Annuloidea.]

A genus of echinoderms.

A class of Echinodermata including the true starfishes. The rays vary in number and always have ambulacral grooves below. The body is starshaped or pentagonal.

One side of an echinoderm, including a pair of ambulacra, in distinction from the opposite side (trivium), which includes three ambulacra.

A large class of Echinodermata, including numerous extinct families and genera, but comparatively few living ones. Most of the fossil species, like some that are recent, were attached by a jointed stem. See Blastoidea, Cystoidea, Comatula.

The class Echinodermata which includes the sea urchins. They have a calcareous, usually more or less spheroidal or disk-shaped, composed of many united plates, and covered with movable spines. See Spatangoid, Clypeastroid. [Written also Echinidea, and Echinoida.]

The Echinodermata.

A genus of echinoderms, including the common edible sea urchin of Europe.

A process by which certain coral polyps, echinoderms, annelids, etc., spontaneously subdivide, each individual thus forming two or more new ones. See Strobilation.

One of the classes of echinoderms.

In echinoderms, one of the areas or zones intervening between two ambulacra. See Illust. of Ambulacrum.

g, or pertaining to, the genus Madrepora. Madreporic plate (Zoöl.), a perforated plate in echinoderms, through which water is admitted to the ambulacral tubes; -- called also madreporic tubercule.

The madreporic plate of echinoderms.

A class of star-shaped echinoderms having a disklike body, with slender, articulated arms, which are not grooved beneath and are often very fragile; -- called also Ophiuroida and Ophiuridea. See Illust. under Brittle star.