A long, thin shell with round ends. Has a thick shiny brown cover (periostracum) which extends beyond the shell edge. When the animal dies this becomes frayed and torn. This is not a true mussel. Grows to 50mm shell length.

Common in low tide zone to 60 m. Buried 10-60 cm deep in in firm sand or mud in harbours and estuaries. Larger individuals are usually found more deeply buried. Often associated with seagrass Zostera muelleri).

Can feed on organic detritus within the sediment, however, most of its nutrition comes from symbiotic bacteria in the gills.

This is the largest of 5 species found in NZ.

NZ Coastal Marine Invertebrates; Vol 1
Photo Credit: Rod Morris. Photos available from www.rodmorris.co.nz