Shell small, subcircular, moderately inflated, slightly longer than high (100L: 88H: 64W), transluscent, white, sculpture limited to small number of co-mar-ginal lines close to shell margin; umbos large, an-teriorly directed and incurved; shell margin smoothly curved from posterior limit of posterior hinge plate to anterior limit of lunule, postero-dorsal margin slightly flattened, antero-dorsal (lunular) margin smoothly curved; lunule somewhat lozenge-shaped, outlined by well-defined incised groove; no escutcheon; ligament opisthodetic, slender, relatively short, partly external, attached to nymph at outer margin of hinge plate; right hinge plate short, moderately broad, cardinal 1 anterior to umbo, forms ventral spoon-shaped shelf, cardinals 3a and 3b ventral to umbo, cardinal 3a overlaps cardinal 1 to slight extent, not clearly separate from cardinal 3b, together they form dorsally spoon-shaped ridgewith angulate posteriormargin, posterior hinge plate short, merging with faintly grooved shell margin, faint interior shell buttress extends anterior to cardinal 1 and marks the perimeter o lunule, antero-dorsal margin slightly grooved below distal half of lunule margin, hinge plate of left valve somewhat broader than right, cardinals 2a and 2b form elongate sinusoidal shelf at ventral margin anterior to umbo, interlocks with ventral surface of cardinals 1 and 3a, cardinal 4 short, ventrally spooned shelf, interlocks dorsal and partly posterior to cardinal 3b, thickened dorsal shell margins interlock with grooves of right valve.

K. biscayensis most closely resembles K. miliaris, K. nitida and K. atlantica but is distinguished from them by the paucity of co-marginal striation, by the more elongate somewhat lozenge-shaped lunule and by the unusually short and characteristic hinge plate

Upper slope depths in the Bay of Biscay, 465–1015m.