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Any one of numerous species of echinoderms of the order Echinoidea.

The five united jaws and accessory ossicles of certain sea urchins.

One of the five arched processes of the shell around the jaws of a sea urchin.

rusting ice come rolling down the flood. Dryden. Cake urchin (Zoöl), any species of flat sea urchins belonging to the Clypeastroidea. -- Oil cake the refuse of flax seed, cotton seed, or other vegetable substance from which oil has been expressed, compacted into a solid mass, and used as food for cattle, for manure,…

Like or related to the genus Clupeaster; -- applied to a group of flattened sea urchins, with a rosette of pores on the upper side.

The shelly skeleton of a sea urchin.

Of or pertaining to the shell of a sea urchin. Coronal suture (Anat.), a suture extending across the skull between the parietal and frontal bones; the frontoparietal suture.

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.]

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

A band of minute tubercles, bearing modified spines, on the shells of spatangoid sea urchins. See Spatangoidea.

A cretaceous fossil sea urchin of the genus Galerites.

A large clavate spine of a fossil sea urchin.

als which make burrows in stone, as many bivalve mollusks, certain sponges, annelids, and sea urchins. See Lithodomus.

A genus of sea urchins, similar to Spatangus, abounding in the chalk formation; -- from the starlike disposal of the ambulacral furrows.

opper occuring in acicular crystals; -- called also aikinite. -- Needle shell (Zoöl.), a sea urchin. -- Needle spar (Min.), aragonite. -- Needle telegraph, a telegraph in which the signals are given by the deflections of a magnetic needle to the right or to the left of a certain position. -- Sea needle (Zoöl.), the…

An extinct order of sea urchins found in the Paleozoic rocks. They had more than twenty vertical rows of plates. Called also Palæechini. [Written also Palæechinoidea.]

An order of Echini, including the irregular sea urchins, as the spatangoids. See Spatangoid.

A sea urchin (Goniocidaris hystrix) having very long spines, native of both the American and European coasts. To pay the piper, to bear the cost, expense, or trouble.

The free-swimming larva of sea urchins and ophiurans, having several long stiff processes inclosing calcareous rods.

g all the parts of the same kind alike in size and shape; as, a regular flower; a regular sea urchin.