Subgenus 1. Sphærozonactis, Haeckel.
Definition.—Spicula radiate, not geminate, consisting of three, four, or more needles or shanks, radiating in different directions from one common central point.
1. Sphærozoum triactinium, n. sp.
Spicula all (or nearly all) triradiate, composed of three (or sometimes in few spicula four) needle-like shanks, diverging from one common point. Shanks straight or somewhat curved, smooth, pointed. Central capsules spherical, with one central oil-vesicle. This species may be regarded as the social form of Thalassoxanthium triactinium.
Dimensions.—Diameter of the central capsules 0.1 to 0.12, length of the spicula-shanks 0.05 to 0.1.
Habitat.—South Pacific, Station 295, surface.
2. Sphærozoum medusinum, n. sp.
Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) needle-like shanks (mostly of unequal length), diverging from one common point. Shanks slightly curved, pointed, thorny, covered with small spinules. Central capsules ellipsoidal, containing several (four to eight) oil-vesicles. This species may be regarded as the social form of the solitary Thalassoxanthium medusinum (Pl. 2, fig. 5).
Dimensions.—Diameter of the central capsules 0.15 to 0.18, length of the spicula-shanks 0.08 to 0.12.
Habitat.—North Pacific, Station 236, surface.
3. Sphærozoum hamatum, n. sp.
Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) needle-like shanks, mostly of very different size, diverging from one common point. Shanks strong, straight, curved, or hook-like; thorny, covered with small spinules on the distal extremity. Central capsules ellipsoidal, large, containing many (ten to twenty) oil-globules. This large species is distinguished by the very irregular form and size of the spicula.
Dimensions.—Diameter of the central capsules 0.2 to 0.25, length of the spicula-shanks 0.12 to 0.18.
Habitat.—Central Pacific, Station 265, surface.
4. Sphærozoum hexactinium, n. sp.
Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in few spicula five or seven) needle-like shanks, mostly of equal size, diverging from one common point in two opposite hemispheres (three needles upwards, three needles downwards). Shanks somewhat curved, pointed,
