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tooth shell:see MolluscaMollusca
, taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
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(also tusk shell), any mollusk of the class Scaphopoda. Body length, 3 mm to 12 cm. The bilaterally symmetrical body is enclosed in a shell that resembles an elephant tusk or a tooth with openings at each end. The tooth shell can project its head and foot out of the anterior opening, the larger of the two openings. Above the base of the head there are folds of skin equipped with bundles of slender tentacles which serve as sensory and food-catching organs. Tooth shells feed on foraminifers and other small sand inhabitants. The sexes are separate, and there is external fertilization. The eggs develop into free-swimming larvae, or trochophores, which descend to the sea bottom in five or six days.
There are two families of tooth shells, comprising approximately 350 species. The mollusks live in seas at various depths, buried in the bottom; as a rule, only the posterior end of the shell protrudes above the sea bottom.
REFERENCESRukovodstvo po zoologii, vol. 2. Edited by V. A. Dogel’ and L. A. Zenkevich. Moscow-Leningrad, 1940.
Zhizn’ zhivotnykh, vol. 2. Moscow, 1968.