Shell minute, white, rather thin, whorls 4. Spire 1 ½ times height of aperture. Protoconch large of two whorls, sculptured with four prominent spiral ridges. Post-nuclear whorls sculptured with oblique bluntly-rounded heavy axials extending from suture to suture and over the entire base, 13 on the body-whorl; there is a heavy spiral ridge at the suture. Aperture obliquely ovate, outer lip thin; peristome continuous over parietal wall as a sharply defined callus.

Height, 0·85 mm.; diameter, 0·45 mm.
Holotype in writer's collection, Auckland Museum (unique).
Locality: 73 fathoms off North Cape, N.Z. (Captain J. Bollons).

The only other described species is the genotype from off Puysegur Point in 170 fathoms, but I have a deformed example of probably a third species from 50 fathoms off the Snares Islands. Laws, 1940 (Trans. Roy. Soc. N.Z., vol. 69, p. 437) records costata from the Waitotaran (Lower Pliocene) of Kaawa Creek, New Zealand.