St Clair Beach is long, sandy, and relatively barren of inter-tidal invertebrates. Except for these old pilings, where some creatures maintain a precarious foothold.
Top-shells nestle in a crack. The popular literature on NZ fauna is not very extensive and old. But I think these are dark top-shells Melagraphia aethiops.
A colony of small black mussels live in slightly more exposed location. Apparently they are considered a southern variety of the European mussel Mytilus edulis. How unromantic!
Whilst in larger crevices a mixed colony of small barnacles, small mussels and some top-shells have found shelter.
Source: New Zealand Shells by John Child, 1974, Fontana, Auckland.
