The genus Rhaphidozoum differs from Sphærozoum by the composition of the skeleton of two or more different kinds of spicula, and has therefore the same relation to it as the solitary Lampoxanthura to Lampoxanthella.
In some species nearly all the different forms, which characterise the numerous species of Beloidea, may be united in one and the same individual.
Subgenus 1. Rhaphidonactis, Haeckel.
Definition.—Spicula of two different kinds; one kind simple, needle-shaped, the other radiate (composed of three, four, or more shanks, diverging from one common point).
1. Rhaphidozoum pelagicum, n. sp.
Spicula of two different kinds; one kind simple thin needles, a little curved or bent, the other kind triradiate, with three thin, curved shanks. Both kinds smooth, without thorns. Resembles a combination of Belonozoum italicum and Sphærozoum triactinium.
Dimensions.—Diameter of the central capsules 0.1 to 0.12, length of the spicula 0.05 to 0.15.
Habitat.—Central Pacific, Station 267, surface.
2. Rhaphidozoum pacificum, n. sp.
Spicula of two different kinds; one kind simple needles, stout and straight, pointed at both ends, the other kind triradiate, with three straight and stout shanks. Both kinds thorny.