Spines formed like a quadrangular double pyramid or an irregular octahedron; the basal leaf-cross being extremely developed, with four very large and thin lamellar leaves; the basal halves of the twenty double pyramids are united by the meeting edges of those leaves, while their distal halves are free, with simple apices. Therefore the four triangular leaves of each spine are equally thinned from the middle towards the two ends.
Dimensions.—Length of the spines 0.1 to 0.2, greatest breadth 0.04 to 0.08.
Habitat.—Central Pacific, Stations 266 to 274, surface.
14. Acanthonia multispina, Haeckel.
Acanthometra multispina, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 47, Taf. vii. figs. 6-9.
Acanthometra multispina, Haeckel, 1862, Monogr. d. Radiol., p. 384.
Spines quadrangular, with four lamellar prominent edges, in the proximal half nearly prismatic, in the distal half pyramidal; both halves separated by a prominent short tooth on each edge. Here in the middle part the breadth (including the four teeth) is equal to the basal leaf-cross. Central capsule opaque, brown.
Dimensions.—Length of the spines 0.2 to 0.3, greatest breadth 0.01 to 0.02.
Habitat.—Mediterranean (Messina); Tropical Atlantic, Station 348.
15. Acanthonia serrulata, n. sp.