Twelve radial spines of equal size, arising from a common central point, and diverging in different directions. The twelve spines are very large, opposite in six pairs, cylindrical, longitudinally striped (the expression of concentric lamellæ), and with spinulate surface, covered with innumerable small thorns. The basal quarter of each spine is straight and simple, the second quarter twice forked, and these four fork-branches are again in the outer half of the spine richly forked or ramified, with diverging, slightly curved thin branches; each of the twelve spines with about sixty to eighty terminal branches, the ends of which seem to fall into a spherical face. The position of this remarkable species in this family is doubtful.
Dimensions.—Length of the spines 0.12 to 0.16, of the simple basal part 0.04.
Habitat.—South Pacific (off Juan Fernandez), Station 299, surface.
5. Polyplagia viminaria, n. sp.
Numerous (sixteen to twenty or more) radial spines of about equal size, arising from a common central point and diverging in different directions, richly and more or less irregularly branched. The ends of the numerous small branches seem to fall into a spherical face. The large spines of this species have the same form and structure as in the preceding, nearly allied species, but are more numerous and more irregularly branched and disposed.
Dimensions.—Length of the spines 0.2 to 0.25, of the simple basal part 0.05.
Habitat.—North Pacific, Station 241, surface.
Family XLVII. Plectanida, Haeckel.
Plectanida, Haeckel, 1881, Prodromus, p. 424.
Definition.—Plectoidea with a wattled skeleton, composed of the meeting and united branches of radial spines, which arise from a common central point or central rod, and protect the partly enclosed central capsule.