111 — Wheel shell, Zethalia zelandica

Zethalia zelandica, north Piha Beach, 27/4/17.
These aren't that common here on the west coast. 

Zethalia zelandica, showing animal and
position in the sand. After Morton & Miller,
1968, p467.

The wheel shell, Zethalia zelandica, * is a small (~20 mm across), gastropod endemic to New Zealand and found throughout the three main islands. They are found off exposed sandy beaches and can wash up in great numbers after storms, particularly on the north eastern coast of North Island.

There are some morphological differences over their range, with examples from Stewart Island being higher in the spire and correspondingly narrower than those from the northeast of North Island. I can remember walking around the base of Mt. Maunganui as a boy and seeing banks of dead shells.

Wheel shells are thought to feed on diatoms and other organic matter; they do this through the ingestion of large amounts of sand, although their ecology isn't really all that well-known.

* (Hombron & Jacquinot, 1854)



More info:


Beu, A. G. & Maxwell, P. A. (1990). Revised descriptions of New Zealand Cenozoic Mollusca.

Morton, J. E. & Miller, M. (1968). The New Zealand seashore. Collins.