Thoristella chathamensis chathamensis

Taxobox
name = "Thoristella chathamensis chathamensis"
status =
regnum = Animalia
phylum = Mollusca
classis = Gastropoda
subclassis = Prosobranchia
ordo = Archaeogastropoda
superfamilia = Trochacea
familia = Trochidae
genus = "Thoristella"
species = "T. chathamensis"
subspecies = "T. chathamensis chathamensis"
trinomial = "Thoristella chathamensis chathamensis"
trinomial_authority = (Hutton, 1873)

"Thoristella chathamensis chathamensis" is a subspecies of small sea snail, a marine gastropod mollusc in the family Trochidae, the top snails or top shells.

Distribution

This subspecies is endemic to New Zealand's Chatham Islands.

Habitat

These top snails are found from low tide to depths of up to 80 m.

Description

The shell of this species is small, solid, broadly conical, with straight sides except for a heavy, rounded peripheral flange-like keel. The base is almost flat. Sculpture consists of flat-topped spiral cords, with linear interspaces, five or six above the keel on the spire, and about eight similar primary cords on the base, often with extra intermediate threads. Weak irregular subsutural axial folds also are sometimes present. The umbilical cavity is small and half filled with callus.

The shell colour pattern is of regular oblong maculations in reddish-brown on the peripheral keel, and interrupted lines in the same colour on most of the spiral cords, the latter resolving into irregular radial streaks. In beach-worn shells, the maculations fade to dark pink or reddish.

The shell height is up to 7.5 mm, and the width is up to 9 mm.

References

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