Appearance
L. alternata is a five-armed sea star with arms that can extend up to 6 in (15 cm) from its center point. The center disk is small, and the arms are relatively narrow. Covering the arms are small spines. The under surface is covered in narrow skeletal plates at right angles to the groove. Each of these plates have two long, slender spines at the margin. The upper aboral side can be gray, brown, greenish, purplish, or black with bands of tan or yellow. The tube feet are often orange.

