Protoconch: ½ whorl with one strong spiral groove, becoming ob¬solete at the beginning of the teleoconch; transition to teleoconch obsolete. Teleoconch: between 1-1V2 whorls; suture well-marked, deep and strongly impressed; last whorl strongly convex with numerous, irregularly spaced, weak axial costulae, becoming ob¬solete at the periphery; costulae somewhat stronger on the first half of the teleoconch; very fine, spiral lirae between the axial costulae. Aperture: subcircular; peristome continuous; inner and outer lips very thin. Colour: transparent, yellowish-brown. Shell-dimensions (in mm): 0.55 - 0.65 Operculum: subcircular, horny, paucispiral with a central nucleus.
Radula: formula. 1-1-0-1-1, each radular row consisting of two dagger-like teeth, articulating at the outside with a very small marginal tooth; basal part of the dagger-like teeth with one very long, sharp and strongly projecting central cusp, and two small lateral projections; basal portion of the marginal teeth subrectangular and flat-sided, presenting one blunt cusp, the latter articulating with the outer lateral projection of the dagger-like tooth.

Ammonicera plicata sp. nov. is most closely related to A. japonica Habe, 1972, but differs from the latter in having a larger and more flattened shell, the axial costulae being weaker and the strong nodules on the ventral and dorsal sides of the shell being absent. Moreover, the protoconch of A. plicata does not show the reticulate sculpture of A. japonica on the outer side. The shell colour is paler in A. plicata sp. nov. than in A. japonica.

Type-locality. — Republic of Maldives, North Male Atoll, Baros Island