Dimensions.—Length of the two major spines 0.1 to 0.4, breadth 0.005 to 0.015; length of the eighteen minor spines 0.005 to 0.15.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
17. Amphilonche acufera, n. sp.
Two principal spines thick, four-sided prismatic in the basal half, cylindrical or spindle-shaped in the distal half, with simple conical apex. Eighteen smaller spines shorter, thin, bristle-shaped or conical on the base. All twenty spines in the centre perfectly grown together, forming a single piece of acanthin. (Derived from Amphilonche elongata by central concrescence.)
Dimensions.—Length of the two major spines 0.3 to 0.5, breadth 0.01 to 0.03; length of the eighteen minor spines 0.08 to 0.2.
Habitat.—Central Pacific, Stations 266 to 274, surface.
Genus 342. Amphibelone,[[382]] Haeckel, 1862, Monogr. d. Radiol., p. 392.
Definition.—Amphilonchida with two unequal principal spines (the frontal spine very different from the caudal spine); the eighteen smaller spines nearly equal.
The genus Amphibelone exhibits among the Amphilonchida the same remarkable differentiation of the two principal or longitudinal spines, as Zygostaurus among the Quadrilonchida; the frontal spine differs commonly from the caudal spine not only in its size, but also in its peculiar form; commonly one pole of the longitudinal axis is much more strongly developed than the other. The eighteen smaller spines are nearly equal.