Dimensions.—Length of the equatorial cross 0.5, breadth 0.4.
Habitat.—Indian Ocean (Madagascar), Rabbe, surface.
4. Zygostaurus caudatus, n. sp.
Frontal spine (c1) very different from the others, pincer-shaped, with two long, nearly parallel slightly bent horns. Lateral spines (c2 and c4) only half as long, with two short, nearly parallel horns. Caudal spine (c3) very long and stout, spindle-shaped, about twice as long as the frontal spine. Eight tropical spines of equal size and form, symmetrical, with two long and thin, divergent horns. Eight polar spines short and stout, with two divergent horns.
Dimensions.—Length of the equatorial cross 0.8, breadth 0.3.
Habitat.—Central Pacific, Station 265, surface.
5. Zygostaurus frontalis, n. sp.
Frontal spine (c1) very different from the others, with two very long, divergent, stout branches. Lateral spines (c2 and c4) only half as long, each with two stout, nearly parallel horns of equal length. Caudal spine (c3) simple, sword-like, shorter than the three former. Eight tropical spines of equal size and form, symmetrical, of the same shape as the two lateral, but only half as large. Eight polar spines very small, rudimentary, each with two short teeth.
Dimensions.—Length of the equatorial cross 0.7, breadth 0.5.
Habitat.—Central Pacific, Station 274, surface.