11. Acanthonia cuspidata, Haeckel.
Spines quadrangular pyramidal, with four prominent lamellar edges, tapering gradually from the broad base towards the simple distal apex. Basal leaf-cross as broad, with a small central pyramid.
Dimensions.—Length of the spines 0.5, basal breadth 0.012; leaf-cross 0.025.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
12. Acanthonia quadrifolia, Haeckel.
Spines in the basal part quadrangular pyramidal, with four prominent lamellar edges and a large basal leaf-cross; in the distal part three to six times as long, cylindrical, of equal breadth. Apex simple, conical, or bifid. Central capsule yellow or whitish. This common species differs from the nearly allied Acanthometron catervatum mainly by the strong development of the large basal leaves or wings.
Dimensions.—Length of the spines 0.3 to 0.5, breadth in the distal half 0.002, in the basal part 0.02.
Habitat.—Mediterranean; North Atlantic, Stations 252 to 254; Færöe Channel, Gulf Stream, in enormous numbers, John Murray, surface and at various depths.
13. Acanthonia diplopyramis, n. sp.
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.
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.
