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Lives of the Other Mollusks 55
microscopic longitudinal or concentric riblets and the nature of the apical
slits are often useful for identification. Few of our American species, other
than a few pinkish or yellowish forms, can boast of colorful shells; but in
the East Indies such forms as Dentaliwn elephantinum Linne are brightly
hued in various shades of emerald green and jade. Some species of Dentalium
have a terminal pipe projecting out of the posterior end.
There are only two families in the class Scaphopoda—the Dentaliidae
and the Siphonodentaliidae. Both families are well-represented in our waters,
the former by numerous species of Dentaliimt, the latter by members of the
genus Cadulus.
Dentaliidae: Shell tusk-shaped, increasing in size regularly with the greatest
diameter at the mouth end. Foot conical. Central tooth of radula twice
as wide as long.
Siphonodentaliidae: Shell bulbous near the middle with the mouth end
generally contracted. Foot vermiform, capable of expansion into a
rosette-like disk at the end. Central tooth of radula almost square.