About Diloma subrostratum (Gray, 1835)
This species, Diloma subrostratum (Gray, 1835), has an adult shell that ranges in length from 11 mm to 32 mm. The shell itself is solid, conical, and suborbicular in shape. It is often more or less black in color, marked with close, wavy longitudinal yellow lines. The spire is short, and contains five whorls. The final (last) whorl is large and rounded, with three to six spiral keels on its hinder portion. The shell axis is imperforated. The interior of the aperture is smooth and silvery. This is a common estuarine species that is endemic to New Zealand, where it is found on the North Island, the South Island, and Stewart Island.
