Zerotula ammonitoides: Shell minute, perfectly discoidal, bicarinate, spire and base slightly concave. Whorls 3 ¼, including a small smooth protoconch of one whorl, the apex slightly inrolled. Upper and lower peripheral keels each bounded by a broad rounded spiral ridge; edge of whorl between the keels vertical, very slightly convex and smooth. Upper and lower surfaces sculptured with close-spaced, strong, rounded radials, 28 on the body-whorl. Aperture quadrate, peristome continuous. Colour uniformly golden brown.

Height, 0·4 mm.; diameter, 1·35 mm. (holotype).

Holotype presented to Auckland Museum.

Locality: 6–10 fathoms Mangonui, Doubtless Bay, N.Z. (W. La Roche).

Off Mangonui, Doubtless Bay, 6-10 fathoms (type). Shell minute, discoidal, very flat, with the spire and base slightly concave. Periphery bicarinate, the carinae smooth and with a slightly concave area between. Sculpture of both upper and lower surfaces consisting of strong rounded radials that do not cross the peripheral keels. Colour uniformly golden-brown. Height 0.4 mm., width 1.35 mm.