Dimensions.—Length of the spines 0.15, breadth in the middle part 0.012, on both ends 0.025.
Habitat.—South Pacific, Station 288, surface.
8. Acanthonia quadrangula, n. sp.
Spines quadrangular prismatic, with smooth prominent straight edges, but of very different breadth in both halves; the inner or proximal half (inside the central capsule) twice to four times as broad as the outer or distal half (outside the central capsule); both ends suddenly separated by a constriction, in which is inserted the membrane of the capsule. The latter is pellucid, with a number of yellow bodies. Apex of the spines simple, base pyramidal, without leaf-cross.
Dimensions.—Length of the spines 0.2 to 0.4, breadth of the basal half 0.01, of the distal half 0.002 to 0.004.
Habitat.—Atlantic, Canary Islands, Azores, Station 354, surface.
Subgenus 2. Acanthonidium, Haeckel.
Definition.—Spines at the central base with a broad leaf-cross, composed of four prominent triangular lamellæ; the meeting edges of these crossed lamellæ between every three or four neighbouring spines so rest one upon another that twenty-two hollow pyramidal compartments are formed (compare p. [721]).
9. Acanthonia echinoides, Haeckel.
Acanthometra echinoides, Claparède et Lachmann, 1858, Études sur les Infusoires et les Rhizopodes, &c., p. 459, pl. xxiii. figs. 1-5.