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.
3. Auloceros capreolus, n. sp. (Pl. 102, fig. 8).
Radial tubes cylindrical, equally broad. Terminal branches in two opposite clustered bunches, each with sixteen to eighteen unequal secondary branches. The total length and breadth of each cluster is about four times as great as the tube is broad. No terminal spathillæ.
Dimensions.—Length of the tube 1.5 to 2.0, breadth 0.03; branches 0.07 to 0.1.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
4. Auloceros cervinus, n. sp. (Pl. 102, figs. 9, 10).
Radial tubes slender, spindle-shaped, slightly curved, tapering gradually from the middle towards the two ends. Terminal branches constantly three, obliquely ascending, each twice or three times forked (often more or less irregularly), with slender, curved, secondary and tertiary branches (twenty to twenty-four on each tube); the latter are scarcely half as broad as the three main branches of each tube. No terminal spathillæ.
Dimensions.—Length of the tubes 2.0 to 3.5, breadth 0.03 to 0.04; branches 0.12 to 0.15 long.
Habitat.—South Atlantic, Station 325, depth 2650 fathoms.
5. Auloceros elegans, n. sp. (Pl. 102, fig. 1).
Radial tubes slender, cylindrical, straight, equally broad. Terminal branches two or three, more or less irregularly branched, each with twelve to eighteen curved and pointed secondary branches. No terminal spathillæ. Differs from the preceding Auloceros cervinus in the cylindrical form of the thinner straight tubes, and the more irregular ramification; the branches are nearly
