CLASSIFICATION OF DENTALIUM
PHYLUM :- MOLLUSCA (Unsegmented bilaterally symmetrical and provided with visceral mass, foot and mantle. )
CLASS :- SCAPHOPODA (Head indistinct, shell tubular and opened at both ends.)
ORDER :- DENTALIIDA
GENUS :- Dentalium (Tusk shell)
They are commonly found in Europe, Pacific coast, New England coast (except polar seas).
HABIT AND HABITAT
Dentalium is marine, living in clean sand in various depths from shallow water to 2,600 fathoms deep.
GENERAL CHARACTERSTICS OF DENTALIUM
- Body called as Elephant’s tusk shell.
- Body of the animal lies in a tubular, bilaterally symmetrical, cylindrical and arched shell secreted by mantle, the concave side representing the upper or dorsal side of the body.
- Body of the animal has a vestigial head, which protrudes as proboscis from shell, without eyes.
- Mouth is surrounded by leaf like tentacles called as captacules having sucker like tips which are sensory, prehensile and can regenerate.
- No ctenidia are present, the tentacles being possibly homologous to them.
- Conical foot also protrudes from shell from anterior end and burrows in sand.
- After removing the shell, internal structures, such as muscles, liver and kidneys are seen. Radula is well developed. Anus behind the base of the foot. Respiration by transverse folds in the lining of the mantle because gills are absent. Circulatory system is poorly developed. Nervous system is simple, consisting of usual cerebral, pleural and pedal ganglia. Eyes are absent.
- Circulatory system is very simple and there is no distinct heart.
- Sexes separate.
The tusk shell was economically very important for Red Indian tribes of America. They used Dentalium indianorum as Sanampum of money (as currency).
The body is enclosed in a tusk shell and it has all above features hence it is Dentalium.