1. Zygostaurus amphithectus, n. sp. (Pl. [131], fig. 7).
Frontal spine (c1) little different from the two lateral spines; each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, spindle-shaped, about as long as the frontal spine. Tropical spines little smaller than the three former, and of the same symmetrical forked form. Eight polar spines much smaller, but also forked, with thin bristle-shaped branches.
Dimensions.—Length of the cross (longitudinal axis) 0.5, breadth (lateral axis) 0.4.
Habitat.—Central Pacific, Station 272, surface.
2. Zygostaurus longicornis, n. sp.
Frontal spine (c1) little different from the two lateral spines, each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, lanceolate, shorter than the frontal spine. Eight tropical spines in the basal part smaller than the three former, but with much longer fork-branches, which are prolonged into very thin and long bristles. Eight polar spines rudimentary, very short.
Dimensions.—Length of the equatorial cross 0.4, breadth 0.3.
Habitat.—South Pacific, Station 295, surface.
3. Zygostaurus cornutus, n. sp.
Frontal spine (c1) little different from the two lateral spines, each with two divergent straight horns, which are shorter than the basal part. Caudal spine (c3) simple, triangular, shorter than the three former. Eight tropical spines of equal size and form, doubly forked, each with four thin, bristle-shaped, little divergent teeth. Eight polar spines short, simply forked.