Diagnosis: Shell high-conical, base convex; 2 rows of 12-20 rounded nodules on last whorl, peripheral nodules crossed by 2-4 threads; columella flared at base, anterior lip rounded; grey or black with white nod¬ules. Penial filament small, narrow, less than half total length of penis; copulatory bursa divided, ventral branch 0.3-0.5 length of dorsal branch.
Shell: Mature shell height 5.4-12.6 mm. Shape conical (H/B = 1.36-1.60; SH = 1.68-2.05); spire whorls slightly rounded, suture distinct; spire profile slightly convex; periphery of last whorl weakly angled; profile of base convex. Columella short, concave, flared and hollowed at base; anterior lip rounded; parietal area not usually eroded; sometimes a slight pseudumbilical chink adjacent to columellar pillar. Sculpture of last whorl: 2 rows of rounded nodules, at periphery and shoulder, axially aligned in 12-20 pairs; suture rugose, sometimes developing into a third row of nodules; entire surface (including base) with 14-19 narrow spiral threads and microstriae, peripheral nodules crossed by 2-4 major threads; basal threads (below peripheral nodules) 4-7, sometimes becoming nodulose. Colour: black to dark brown (fading to blue-grey), paler at suture and on base, nodules white; aperture dark brown with pale band at base; columella dark brown.

Range: Marquesas Is and possibly Tuamotu Is.
Habitat: On basaltic rocks in the littoral fringe, on shores of oceanic high islands.
Remarks: The distance of 7-8000 km between the distributions of E. marquesensis and those of other members of the E. malaccana group to the west is too great to be traversed by dispersal of pelagic larvae under present-day conditions of current flows. However, during low sea-level intervals in the past it is possible that distributions of oceanic species such as E. cecillei or E. wallaceana extended further across the Pacific Ocean, if they inhabited the shores of islands that are now partly or entirely submerged. The volcanic islands of the Marquesas group began to form 5.8 Ma (Brousse et ah 1990), and the estimated age of E. marquesensis is in the range 4-8 Ma (Williams & Reid 2004). The present isolation of the Marquesas Islands is a consequence of oceanic currents in the region, and is reflected in both high endemicity of marine fauna (estimated at 10-20%) and intraspecific phylogeographic structure (Randall 1998; Planes & Fauvelot 2002). The sister-species relationships of this species are not resolved by COI sequence data (Williams & Reid 2004; Reid et al 2006).