CASK or TUN SHELL
This fish has a large frail shell, strongly corrugated. It grows up to 9 in. in height and has a very large aperture. Occasionally these shellfish wash up alive on Northland beaches, but they live in from five to 50 fm on sandy or muddy bottom. These shells are more characteristic of warmer seas, and our species, which is closely allied to an Eastern Australian one, undoubtedly reached here per medium of the East Australian warm-water current.
by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.