Habitat.—Central Pacific, Station 274, surface.
2. Polyplagia octonaria, n. sp.
Eight radial spines, straight, three-sided prismatic, of equal size, arising in two opposite groups from the two poles of a short common middle rod (as in Sphærozoum arborescens, Pl. [4], fig. 8, and in other Beloidea). The four spines of each group are divergent, six to eight times as long as the middle rod, each spine armed with three to four verticils of thorny branches.
Dimensions.—Length of the spines 0.15, of the middle rod 0.022.
Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.
3. Polyplagia novenaria, n. sp.
Nine radial spines of equal size, straight, cylindrical, lying nearly in a horizontal plane, or forming a very flat pyramid. Near the common central point every three spines arise from a short common rod, so that the centre of the skeleton is triradial. Each spine bears towards the apex two divergent straight lateral branches. This species may have been derived from Plagiacantha arachnoides by shortening and reduction of the basal parts of the three original branched primary spines.
Dimensions.—Length of the nine spines 0.24, of the three basal rods 0.02.
Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray, surface.
4. Polyplagia duodenaria, n. sp.