Barythaerus biconvexus is a marine bivalve mollusc of the family Thraciidae. It is endemic to New Zealand, with records off southern South Island and Stewart Island.
Barythaerus biconvexus measures up to in length. It is known from depths between , with live specimens from bryozoan and shell substrates at intermediate depths (55–183 m).
References
Further reading Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979