Examples: Gastropods
Worm shell (West Indian worm shell, variable shape, [2, p. 49])
[alpha=83, beta=8, phi=55, mu=10, Omega=2, A=180, a=16, b=16, L=0]
(Click with the mouse over the picture to rotate it)
All worm shells, or
vermetidae, as their name suggests, are irregularly coiled and resemble worm tubes. They are unusual shells which look like
long tubes, evenly spirally coiled at the apex and then loosely and irregularly so. They first grow like typical snails
(in their earlier growth stages, some are almost indistinguishable from turritella and their anatomy shows they are related) but then cement
themselves to a hard substrate
and begin twisting and meandering unpredictably (generally coil upon themselves).
The worm shell of West Indies, although grouped with other worm shells, is actually a screw shell which has unwound itself, a point proved
if you examine the animal that formed it.
Habitat: sand or in sponges, West Indies.
[2] S. Peter Dance, Shells, Dorling Kindersley, 2002.
