Subgenus 1. Auloceræa, Haeckel.
Definition.—Distal ends of the terminal branches pointed, smooth, without spathilla (or corona of radiate denticles).
1. Auloceros furcosus, n. sp. (Pl. [102], figs. 2-6).
Radial tubes slender, spindle-shaped or nearly cylindrical, more or less tapering towards the two ends. Terminal branches slender, curved, twice to four times as long as the tube is broad, very variable in number (usually two or three, rarely four, five, or six; compare figs. 2-6), once or twice forked; the secondary branches are short, irregular, and pointed. No terminal spathillæ. In some specimens of this species all the tubes bear two or three terminal branches, whilst in others there are tubes with four, five, or six branches intermingled. When the number of the terminal branches is constant in single localities, this transformistic or "Darwinian" species may be divided into the following "subspecies:" (1) Auloceros pandora (with variable numbers); (2) Auloceros bifurca (fig. 2); (3) Auloceros trifurca (fig. 3); (4) Auloceros quadrifurca (fig. 4); (5) Auloceros quinquefurca (fig. 5); (6) Auloceros sexfurca (fig. 6).
Dimensions.—Length of the tubes 1.5 to 2.5, breadth 0.02 to 0.03; branches 0.05 to 0.15 long.
Habitat.—North Pacific, Stations 231 to 253, surface and at various depths.
2. Auloceros trigeminus, n. sp. (Pl. [102], fig. 7).
Radial tubes club-shaped, gradually thickened towards the inflated distal end. Terminal branches short, scarcely longer than the tube is broad, two constantly opposite, each with three equal, conical, short secondary branches. No terminal spathillæ.
Dimensions.—Length of the tubes 0.6 to 0.8, breadth 0.02 to 0.03; branches 0.04 to 0.08.
Habitat.—North Atlantic, Station 353, depth 2965 fathoms.