DIAGNOSIS. Shell: Spire moderately tall; body whorl weakly convex, expanded beyond line of flat spire whorls, with short spines and simple suture. Teleoconch of about 5 whorls, all with numerous, short, hollow spines on periphery, 15 on last two whorls. Body whorl almost evenly convex (peripheral and basal angulations very weak), basal angle marked by a row of gemmules slightly stronger than other basal sculpture on first 1/3 of body whorl, indistinguishable on remainder of whorl. Sculpture of closely spaced rows of rather coarse gemmules, 12 on shoulder of body whorl, 3 between peripheral and basal angles, about 13 on base, becoming coarser towards columellar region. Basal callus small, occupying approximately 1/5 of base, thin, transparent. Colour pale lemon-yellow, with regular, rather large, radial, brown blotches on shoulder (6 on body whorl) and a few very small pale brown specks on base; columellar callus bright lemon-yellow behind columella, whitish where spread on base. Outer lip bright lemon-yellow. Operculum: Oval, white, simple, with weakly wrinkled surface.
DIMENSIONS. Holotype: height 27 mm, diameter (excluding spines) 29 mm, (including spines) 32 mm.
TYPE LOCALITY. 15°24.5'S, 46°02.0'E, off Majunga, N.W. Malagasy Republic, 250-265 m; A. Crosnier Colin.
HOLOTYPE. AMS, C. 112907.
B. flava differs from B. tamikoana in its shorter spire which gives the subspecies a more ovate outline, finer spiral sculpture and a weaker basal angle. The colour patterns of the two subspecies are similar but the basic colour of B. flava is lemon-yellow whereas in B. tamikoana it is fawn. The two forms are here recognized as geographic subspecies because of their general morphological similarity, their wide geographic separation and because the observed differences in shell characters are much greater than between widely separated populations of B. tamikoana.