Cantharidus opalus opalus is a subspecies of large sea snail, a marine gastropod mollusc in the family Trochidae.

Distribution

This subspecies is endemic to New Zealand including the Snares Islands.

Habitat

This top snail lives on coarse brown seaweed at low water and below.

Shell description

The shell is a large, tall-conical, with a broadly rounded periphery. The surface is almost smooth, except for subobsolete linear spiral grooves on the upper whorls, and a few on the lower base, as well as faint axial lines of growth.

The external coloration of the shell grades from russet or orange on the early whorls, to mauve below, the whole crossed by closely spaced zigzag narrow axial stripes in darker mauve. The interior of the aperture is iridescent in a range of bright greenish, bluish and reddish colours.

The shell height is up to 43 mm, and the width is up to 28 mm.

References

• Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1