7. Acanthometron pellucidum, J. Müller.
Spines cylindrical, very thin and long, needle-shaped, nearly of equal thickness in their whole length. Central base with a small fulcral pyramid, without leaf-cross. Distal apex bifid or bifurcate, with two thin parallel teeth. Central capsule pellucid, colourless, with yellow pigment-bodies. (Differs from Acanthometron elasticum mainly in the bifid apex.)
Dimensions.—Length of the spine 0.1 to 0.3, breadth 0.002 to 0.004.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
8. Acanthometron wageneri, Haeckel.
Spines cylindrical, in the thickened outer half about twice as broad as in the thin inner half. Central base a little thickened, with large fulcral pyramid, but without leaf-cross. Distal apex bifid, with two divergent, often denticulated teeth. Central capsule pellucid, with yellow pigment-bodies. (Differs from Acanthometron dolichoscion mainly in the bifid apex.)
Dimensions.—Length of the spines 0.2 to 0.5, breadth in the inner part 0.003, in the outer 0.006.
Habitat.—Adriatic Sea; Triest, Wagner; Corfu, Haeckel, surface.
Subgenus 2. Phyllostaurus, Haeckel, 1862, Monogr. d. Radiol., p. 381.
Definition.—Spines at the central base with a broad leaf-cross, composed of four prominent triangular lamellæ; the meeting edges of the neighbouring lamellæ are propped one upon another in such a manner that there are formed twenty-two hollow pyramidal spaces or compartments (compare p. 721).
9. Acanthometron siculum, Haeckel.
Spines elongate, conical, tapering gradually from the thick base towards the simple distal apex. Conical circular base supported by a basal leaf-cross of double the breadth. Central capsule yellowish-brown, opaque.
Dimensions.—Length of the spines 0.3 to 0.4, basal breadth 0.008 to 0.012, leaf-cross 0.024.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
