44 — Octogonal murex shell, Murexsul octogonus

Murexsul octogonus, Kohimarama Beach,
Auckland 2/04.

Murexsul octogonus, Kohimarama Beach,
Auckland 2/04.

Murexsul octogonus, Kohimarama Beach,
Auckland 2/04.

The octagonal murex (Murexsul octogonus (Quoy & Gaimard, 1833)) is so named because when you down on the spire from the above the sequence of varices (growth ridges) makes the shape of an octagon. They are found in shallow water in the north of New Zealand and can have quite spectacularly spiny shells.

This shell is from off Pakiri Beach, north of Auckland. However, it was actually found on one of the inner city beaches at Kohimarama Beach. This is because that beach was having its sand replenished using sand taken from off Pakiri Beach from depths of about 20–30 m.

The ecology of octagonal murexes is not that well known, but it is thought that they predate bivalves by boring through their shells (like other members of the Muricidae). This species used to be seen more often in the Auckland region and Morton & Miller (1968) describe it a being part of the lower intertidal assemblage of gastropod predators. These days they're not seen that often.
















More info:

More pictures: http://www.mollusca.co.nz/speciesdetail.php?speciesid=996&species=Murexsul%20octogonus

Morton, J. E., & Miller, M. M. 1968. The New Zealand Sea Shore. Collins.