Shell minute, smooth, light olive-brown, obliquely triangularly ovate, inflated. No sculpture, either radial or concentric. Valve margins smooth. Umbones prominent, prodissoconch oval, flattened on top and defined by a slight rim. Hinge strong, closely similar to that of Pronucula. Teeth few, large, squarish, distant from the large almost perpendicular chondrophore. In the right valve there are four strong anterior teeth and two weak ones posterior to the chondrophore. In the left valve there are four strong anterior, and one weak posterior tooth. The posterior subdorsal margin of the right valve fits into a well marked corresponding groove in the left.
Length, 1.15 mm.; height, 1 mm.; thickness (2 valves), 0.61 mm. Holotype: In Auckland Museum.
Localities: Rosa Island, Port Pegasus, Stewart Island (shell-sand, Mrs. R. H. Harrison); Mason's Bay, Stewart Island (shell-sand).