They are rather drab coloured square-backed crabs. The eyes are on short stalks. Commonly it 18mm across the carapace (the back) but can be up to 40mm.

It is very active and digs very complex burrow and tunnels in the mud. They are very common on mudflats and in tidal creeks.

They can often be seen at low tide, cleaning the burrow and sifting through the mud for food or it may feed on bleached sea lettuce.

It has keen eyesight and can detect movement as far as 45m away. Often preyed upon by Kingfishers.
Was Helice crassa

Collins: Gunson Raupō Pocket dictionary of modern Maori Davie, P. (2010). Austrohelice K. Sakai, Türkay & Yang, 2006. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=439866 on 2010-11-22