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A class of marine cephalate Mollusca having a tubular shell open at both ends, a pointed or spadelike foot for burrowing, and many long, slender, prehensile oral tentacles. It includes Dentalium, or the tooth shells, and other similar shells. Called also Prosopocephala, and Solenoconcha.

An order of gastropod Mollusca having a heart with two auricles and one ventricle. The shell may be either spiral or shieldlike.

An order of lowly organized Mollusca belonging to the Isopleura. A narrow groove takes the place of the foot of other gastropods.

Of or pertaining to the mouth and the stomach; as, the stomatogastric ganglion of certain Mollusca.

An extensive division of gastropod Mollusca in which the loop or visceral nerves is twisted, and the sexes separate. It is nearly to equivalent to Prosobranchiata.

ons of either the animal, or vegetable kingdom, as, in zoölogy, the Vertebrata, Tunicata, Mollusca, Articulata, Molluscoidea, Echinodermata, Coelentera, and the Protozoa; in botany, the Phanerogamia, and the Cryptogamia.

An order, or suborder, of gastropod Mollusca in which the gills are usually situated on one side of the back, and protected by a fold of the mantle. When there is a shell, it is usually thin and delicate and often rudimentary. The aplysias and the bubble shells are examples.

especially Ianthina, Murex, and Purpura. See the Note under Purple, n., 1, and Purple of mollusca, under Purple, n.

Having but one gill, as certain molluscs.