THE TOOTH SHELLS CLASS SCAPHOPODA. Shell tubular, tapering, curved, open at both ends; 1 to 5 inches long; body elongated, curved, symmetrical, attached to shell by muscles near posterior end; mantle lines shell, forms tube which flares at anterior end; surface absorbs oxygen, acting as organ of respiration; head rudimentary; eyes none; foot long, pointed; mouth at base of foot contains radula; filaments for seizing food are grouped at corners of mouth; stomach and intes tine simple; liver large, two-lobed, much-branched; kidneys, two, large; reproductive gland large, much elongated in posterior end of shell, discharges through right kidney; sexes separate; heart rudimentary, one-chambered; arteries none; gills none; brain a very small ganglion, connected with four others. Food, small
infusorians and other microscopic organisms. Habitat, sandy or muddy sea bottom, from shallows into very deep water. Distribution world-wide in seas. Shells used for money and for personal adornment by primitive tribes.