Page:Scientific results HMS Challenger vol 18 part 1.djvu/996

788 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.

Definition.— 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.

Definition.—All twenty spines separate, but in contact in the centre and resting one against another by the triangular sides of their pyramidal bases, without a prominent basal leaf-cross.

1. Amphibelone aciculata, n. sp.

Two principal spines thick, without edges and wings, the frontal spine short, spindle-shaped, the caudal three to six times as long, cylindrical, both of equal breadth, with simple conical apex and simple pyramidal base, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, of the same length as the frontal spine. Central capsule cylindrical or spindle-shaped, enveloping the two principal spines nearly throughout their whole length.

Dimensions.—Length of the frontal spine 0.2 to 0.4, of the caudal spine 1.0 to 2.0; breadth of both 0.01; length of the eighteen smaller spines 0.1 to 0.3.

Habitat.—South Atlantic, Station 325, surface.