Barnea similis, a rock borer or piddock, is a marine bivalve mollusc in the family Pholadidae, endemic to New Zealand. It is found around all three main New Zealand islands, plus the Chatham Islands, boring into soft rock and mudstone in the intertidal zone. It is more common in the north.
The shell is large, elongated, tapered behind, and sculptured with concentric ridges, crossed by radial ribs over the front end of the shell, which is widely gaping underneath.
A tiny bivalve, Arthritica crassiformis, cohabits with Barnea similis, groups of two or three individuals occurring along the edge of the piddock's fleshy mantle.
Length is up to 86 mm, and height 32 mm.
- Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1
- Glen Pownall, New Zealand Shells and Shellfish, Seven Seas Publishing Pty Ltd, Wellington, New Zealand 1979 ISBN 85467 054 8
- Miller M & Batt G, Reef and Beach Life of New Zealand, William Collins (New Zealand) Ltd, Auckland, New Zealand 1973