Shell large, dark brown, turreted. Spire elongate approximately two-thirds the length of shell, whorls of which are rounded but somewhat angulated at about the centre. Body-whorl more conspicuously nodosely angulated but angle nearer to suture. Sculptured with oblique, longitudinal ribs and numerous somewhat irregular concentric ridges. Interior brown, white towards the outer lip which is strong, sinuate posteriorly and margined with dark brown. Aperture almost circular, anterior canal short, rather broad; columella curved, inner lip reflected; operculum brown, flat. Size: 3 inches.

A remarkable, dark brown turreted shell, the only species of the genus in Victoria and easily recognized. The nearest ally is Velacumantus australis (Quoy & Gaimard), but immedaitely separated by its smaller size. This shell will aways possess a sentimental interest to Australian naturalists since it is one of the half dozen shells collected by Captain Cook at Botany Bay in April, 1770.

A species which appears in countless numbers in many parts of New South Wales and Queensland, it inhabits estuaries of rivers, mud-flats and mangrove-swamps near the sea. Extremely gregarious and after receding tides their crossing and recrossing tracks form amazing patterns. It is not infrequent to see young oysters adhering to these Mud Whelks. The animal was used as an article of food by the aborigines, many examples appearing in kitchen middens. Toondah was the name given to the shell by aborigines of Moreton Bay, Queensland. It is recorded also from Tasmania. For many years known as Potamides ebeninus Bruguiere.