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One of the grand divisions of the animal kingdom, including the classes Cephalopoda, Gastropoda, PteropodaScaphopoda, and Lamellibranchiata, or Conchifera. These animals have an unsegmented bilateral body, with most of the organs and parts paired, but not repeated longitudinally. Most of them develop a mantle, which in…

A mollusk; one of the Mollusca.

That division of the Mollusca which includes the bivalve shells, like the clams and oysters; -- so called because they have no evident head. Formerly the group included the Tunicata, Brachiopoda, and sometimes the Bryozoa. See Mollusca.

A division of Mollusca remarkable for the bilateral symmetry of the organs and the arrangement of the nerves.

A division of nudibranchiate Mollusca, in which the gills form a wreath or cluster upon the posterior part of the back. See Nudibranchiata, and Doris.

uscles attached to the inner surface, as in the clam, -- or by one, as in the oyster. See Mollusca.

A glandular organ of bivalve mollusca, serving in part as a kidney.

Of or pertaining to the lowest subdivision of the rocks of the Silurian or Molluscan age; -- sometimes described as inferior to the Silurian. It is named from its development in Cambria or Wales. See the Diagram under Geology.

A genus of oceanic heteropod Mollusca, having a thin, glassy, bonnet-shaped shell, which covers only the nucleus and gills.

A large division of Mollusca, including all except the bivalves; -- so called because the head is distinctly developed. See Illustration in Appendix.

The highest class of Mollusca.

A group of nudibranchiate Mollusca having on the back papilliform or branched organs serving as gills.

A division of Mollusca having slender, cirriform appendages near the mouth; the Scaphopoda.

A soft tactile appendage of the mantle of many Mollusca, and of the parapodia of Annelida. Those near the head of annelids are Tentacular cirri; those of the last segment are caudal cirri.

That class of Mollusca which includes the bivalve shells; the Lamellibranchiata. See Mollusca.

The science of Mollusca, and of the shells which they form; malacology.

Having a head; -- said of most Mollusca; -- opposed to acephalous.

Pertaining to the epipodium of Mollusca.

One of the classes of Mollusca, of great extent. It includes most of the marine spiral shells, and the land and fresh-water snails. They generally creep by means of a flat, muscular disk, or foot, on the ventral side of the body. The head usually bears one or two pairs of tentacles. See Mollusca. [Written also Gasterop…

The division of Mollusca which includes the land snails and slugs.