Enoplochiton niger (Barnes 1824)

Animal very large in size, up to 190 mm in examined specimens. Tegmentum dark chocolate-brown, shiny, but easily eroded. Anterior valve with 4–6 concentric, zig-zagged furrows. Lateral areas elevated, well defined by strong round rib at diagonal line, with zig-zagged furrows as on anterior valve. Central areas well defined, smooth jugum bordered by narrow, depressed area with irregular, short, oblique furrows; para-jugal area smooth; pleural area with longitudinal, parallel furrows, not usually reaching anterior border of valve. Girdle thick, muscular; dorsal surface dark brown, conspicuously dotted with light brown scales, scales irregular in size (larger in middle 1/3 of girdle), up to 1.5–2 mm long in specimens 50 mm long (larger in larger specimens), vaguely striate, usually eroded at upper edge, clearly separated from each other by area as wide as scale; on outer 1/5 of girdle, scales much smaller, shorter, dark brown, erect, spine-like; girdle surface completely covered otherwise with minute, dark brown, lanceolate spicules, up to 100 μm long, 25 μm thick. Girdle bridges, empty in middle third, but crowded with small, dark brown spiculoid elements (akin to those on girdle proper) in outer thirds (After Ferreira 1986).

This species is confined to the western temperate coast of South America, from Talara, Peru (04°34’S; 81°16’W) to Coquimbo Bay, Chile (29°57’S; 71°20’W). Its bathymetric range is limited to the intertidal zone (Ferreira 1986).