Zygacantha dichotoma, Haeckel, 1862, Monogr. d. Radiol., p. 381.
Acanthometra dichotoma, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 50, Taf. ix. fig. 5.
Spines compressed, pincer-shaped, cleft nearly throughout their whole length into two thin parallel straight rods or fork branches, which are united only in their middle by a narrow bridge, and at their central base by the pyramidal small central apex; above this pyramid each rod is divided into two broad triangular leaves, forming a large basal leaf-cross. Central capsule purple, with yellow bodies.
Dimensions.—Length of the spines 0.1 to 0.15, breadth 0.01 to 0.02.
Habitat.—Mediterranean (Nice), J. Müller, surface.
6. Zygacantha complanata, n. sp.
Spines compressed, two-edged, linear, of equal breadth throughout their whole length. Apex bifid. Base thickened, with a large leaf-cross. (Similar to Amphilonche complanata, but different in the equal size of all twenty spines, which are somewhat broader.)
Dimensions.—Length of the spines 0.12 to 0.18, breadth 0.002.
Habitat.—North Pacific, Station 244, surface.
7. Zygacantha semicompressa, Haeckel.