Diagnosis: Shell high-conical, spire profile straight to slightly convex, base slightly convex; 2 rows of 9-18 rounded nodules on last whorl, peripheral nodules crossed by 2-3 threads, threads on base often nodulose; aperture rounded anteriorly, anterior lip not projecting; grey or black with white to cream nodules. Penial filament triangular, pointed, 0.4-0.5 total length of penis; copulatory bursa divided, ventral branch equal to or longer than dorsal branch.
Shell: Mature shell height 5.0-16.6 mm. Shape conical to high-conical (H/B - 1.34-1.88; SH = 1.63-2.59); spire whorls almost flat to lightly rounded, suture not distinct; spire profile straight to slightly convex; periphery of last whorl rounded; base profile slightly convex. Columella short, concave, hollowed but not flared at base, anterior lip rounded (slightly projecting in juveniles); usually a small eroded parietal and pseudumbilical area. Sculpture of last whorl: 2 (rarely 3) rows of rounded nodules, at periphery and shoulder, axially aligned in 9-18 pairs, occasionally fused to form axial ribs in strongly sculptured shells; entire surface (including base) with 12-26 narrow spiral threads and microstriae, peripheral nodules crossed by 2-3 major threads; basal threads (below peripheral nodules) 3-8, often bearing small nodules. Protoconch 0.28-0.30 mm diameter, 2.6-2.7 whorls. Colour: black to dark brown (fading to blue-grey), paler at suture and on base, nodules white to cream; sometimes black with three cream spiral bands corresponding to two rows of nodules and band on base; aperture dark brown with pale band at base, sometimes two additional pale bands above; columella dark brown.

Comparisons among the five species of the E. malaccana: Aside from the genetic data, the most obvious differences are in distributional range, for only at six localities in western Sulawesi, Ambon and the central Philippines are two (E. malaccana and E. wallaceana) known to be sympatric. There is a striking contrast in habitat type; both E. malaccana and its sister E. austrotrochoides are found on productive, nutrient-rich continental coastlines and are tolerant of some freshwater influence and turbidity, whereas the remaining three are found on oceanic coasts with regimes of low productivity (Rutgers University Primary Productivity Study). Differences in the shell are too slight to be diagnostic, although some trends can be seen. In comparison with E. austrotrochoides the shell of E. malaccana often shows a more con¬vex spire and base, and the columella is not flared or projecting (except in immature shells). Where they are sympatric, E. malaccana shows small nodules on the basal ribs, whereas E. wallaceana does not, but this distinction is not consistent across their ranges. The shape of the penial filament is strikingly large and elongate in E. wallaceana, narrow in E. marquesensis and small in E. cecillei, although in the last of these there is variation that overlaps with all of the other taxa. The filament of E. austrotrochoides is often slightly more sharply tapered at the tip than the triangular filament of E. malaccana. In females, the copulatory bursa is undivided in E. wallaceana, but bifurcates into ventral and dorsal branches in the others. The ventral branch is as large or larger than the dorsal in E. malaccana and E. austrotrochoides, but much smaller in E. marquesensis and of intermediate size in E. cecillei.
Members of the E. natalensis group can be extremely similar in shell characters to the E. malaccana group. In E. natalensis the shell is slightly broader than in the E. malaccana group and there are usually three rows of sharp nodules on the last whorl (not two as in the E. malaccana group). Echinolittorina omanensis is even more similar in outline, but again often bears three, not two, rows of nodules. Nodulose forms of E. pascua are distinguished by the short, recurved columellar base, partial fusion of the nodules to form axial flanges, concave profile above the shoulder, absence of such conspicuously white nodules, stronger and more regular spiral threads over the surface, and presence of a single row of small nodules of the base.

Range : India, mainland coast of Southeast Asia, Southern China, Taiwan, Philippines, Borneo, Sulawesi.
Habitat and ecology: This species is common in the upper littoral fringe, reaching higher levels than any sympatric congener. It has been found on basalt, volcanic tuff, granite, shale, coral limestone, sandstone, concrete and rarely on mangrove trunks, in sheltered to moderately exposed sites. It is most abundant in continental settings, and is more tolerant of turbidity and slightly estuarine conditions than any other Echinolittorina in the IWP. It is generally uncommon on karstic limestone in clear-water habitats with fringing reefs, as in the Philippines and Sulawesi.