A unique shell for the south coast of Florida, B. blainei reaches about 30mm, has a spire angle of 24 degrees, and is white all over. It has spiral sculpture consisting of 13 strong, cord-like costae which are reflected backward and by spiral sculpture consisting of seven ridge-like lines, quite apparent. Although the spiral lines do not cross them, the costae have "sympathetic" points where the spiral lines would cross. The suture is deep. There is a basal ridge. No umbilicus. Though Clench and Turner compared this species with both B. magellanica and B. greenlandica, from which is significantly different, they failed to compare it to B. zelebori, a New Zealand species which is close to identical.