Shell somewhat pyriform, broadly shouldered, small for group, attaining 17+ mm in length (holotype); spire weakly extended; protoconch of 3 whorls, erect and papillate; 4+ postnuclear whorls cancellated, with 12 strong spiral cords, crossed by 16 prominent axial ridges (varices); juncture of spiral cords and varices with a blunt, weakly hooked spine, spines most conspicuous at the shoulder: intervarical pits with 6 to 10 weakly raised striae; parietal shield small, largely confined to columella wall, with outer margin raised and covered with numerous small pustules, mostly pimplelike; outer lip narrowly thickened, crenulated and toothed with about 10 major denticles on the inner labial surface; 3 minor denticles near anterior end of siphonal canal; anal sulcus weakly notched; siphonal canal short, gently recurved, open.
Color-Nucleus shiny, pinkish-tan; postnuclear whorls with creamish tan base color, 4 discontinuous purplish-brown bands on body whorl (1 band on shoulder, 2 on either side of midbody area, and 1 near the base; bands less interrupted on paratype with juvenile aperture ; darkest coloration of bands on the apertural sides of varical spines and at base of outer lip; parietal shield poorly glazed, with white pustules; labial margin white, not blotched.
Type locality-West reef of Kwajalein Atoll, between the islands of Kwajalein and Ninni, Marshall Islands, in about 15 meters, on sandy rubble under coral boulders, along the ocean side dropoff of the fringing reef (teste D. J. Mac-Donald, February 23, 1981).
Distribution - Known only from the type locality.
Etymology—Named for the collector, D. J. MacDonald. He recognized the uniqueness of this discovery and submitted specimens to Robert W. Morrison, who in turn kindly transmitted the material to me for study.
Remarks-Somewhat resembling a tiny, immature Morum (0.) macandrewi (Sowerby, III, 1889), this distinctive species is the first representative of the genus reported from the Marshall Islands. The molluscan fauna of these atolls is well known (e.g. Dietrich and Morris, 1953; Brost and Coale, 1971). The difficulties of collecting on the ocean side of the reefs and the diminutive size of the shells undoubtedly have contributed to the failure to find specimens in the past. No specimens were obtained inside the lagoon. Mr. MacDonald reports examining about a dozen specimens, including two living ones discovered at night on patches of sand near coral rubble. None of the six specimens recorded here were live-taken, but several were obtained in a well-preserved condition, as is the case of the holotype and the figured paratypes.

Kwajalein. Marshall Eilanden.