Diagnosis: Shell angled at shoulder and periphery, with spiral threads and 2-4 raised or carinate, sometimes nodulose, ribs on last whorl; spire whorls with marked shoulder angle; surface dull because of fine spi¬ral microstriae; brown with white dashes or nodules on prominent ribs.
Shell : Mature shell height 4.9-13.6 mm. Shape high turbinate (H/B = 1.33-1.56, SH = 1.49-1.79); spire whorls angled at shoulder, suture distinct; spire profile almost straight; last whorl angled at shoulder and slightly at periphery. Columella long, straight, wide, only slightly hollowed at base; inner lip of aperture smoothly rounded and continuous with eroded pseudumbilical and parietal area. Sculpture of last whorl: surface covered by sharp spiral threads of unequal size, 6-9 below periphery, 16-23 above; usually 2-4 prominent or carinate ribs (at shoulder and periphery only, or shoulder, mid-whorl, periphery and on base) that may bear 14-20 elongate nodules or irregular granules; occasionally only shoulder rib is prominent or ribs absent; surface made dull by fine spiral microstriae. Protoconch not seen. Colour: dark brown, fading to fawn or blue-grey in larger specimens; cream band on base, and area extending to columella usually also pale; the prominent ribs with cream nodules and brown spots between; aperture dark brown with cream band at base; columella pale to dark purple-brown, inner lip purplish.

This is the sister species of E. leucosticta (see Remarks on that species). Shells are, however, more similar to those of E. tricincta. Compared with that species, the shells of E. biangulata are frequently carinate, rarely granulose, and (if present) the nodules are rounded and laterally elongate; shells off. tricincta are seldom carinate, often finely granulose, and nodules (if present) are pointed. Nevertheless, these species are sometimes indistinguishable morphologically from each other, and from rare examples of E. philippinensis

West coast of Sumatra, south coast of Java, Bali.
Remarks: This is one of the rarest littorinids in collections and has seldom been mentioned in the literature, but this reflects its restricted and relatively inaccessible distribution. It is apparently common in its range. This species is found on the exposed oceanic coastlines of Indonesian islands facing the Indian Ocean, where primary productivity is low for most of the year. Beginning in June, monsoon-driven upwelling occurs on the coast of Java, moving westwards to central Sumatra before disappearing in November (Susanto et al. 2001). An almost identical distribution is shown by E. sundaica, although this has not been recorded as far north as Pulau Nias .
Habitat: On wave-exposed basaltic rocks and sea walls in splash zone.