3. Zygacantha compressa, Haeckel.
Spines in the proximal half compressed, broad lanceolate, four to six times as broad as in the thin cylindrical distal half. Apex simple or short bifid. Base pyramidal, thickened, without leaf-cross. No middle rib. Central capsule opaque, yellowish or reddish-brown.
Dimensions.—Length of the spines 0.3 to 0.5, breadth of the inner half 0.015 to 0.02, of the outer half 0.002 to 0.003.
Habitat.—Mediterranean (Messina); Atlantic (Canary Islands), Station 352, surface.
4. Zygacantha furcata, J. Müller.
Acanthometra furcata, J. Müller, 1856, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 499.
Acanthometra furcata, Haeckel, 1862, Monogr. d. Radiol., p. 380.Spines compressed, fork-shaped, divided by two thickened knots into three sections of nearly equal length; middle section broader than the proximal, but smaller than the distal section, which is cleft by a deep fissure into two long parallel straight branches. Base pyramidal, without leaf-cross. Central capsule purple, with yellow bodies.
Dimensions.—Length of the spines 0.1 to 0.15, basal breadth 0.003 to 0.005, distal breadth 0.02 to 0.03.
Habitat.—Mediterranean (Cette). J. Müller, surface.
Subgenus 2. Zygacanthidium, Haeckel.
Definition.—Spines at the central base with a cross of four prominent leaves; the meeting edges of the neighbouring lamellæ so rest one upon another that twenty-two hollow pyramidal compartments are formed (compare p. 721).
5. Zygacantha dichotoma, Haeckel.
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.
