1. Plagiacantha arachnoides, Claparède.
Plagiacantha arachnoides, Claparède, 1858, Études sur les Infusoires et les Rhizopodes, p. 462 (pl. xxii. fig. 8).
Acanthometra arachnoides, Claparède, 1855, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 675.Spines straight, cylindrical, divided into three divergent straight branches of equal size; each branch two to three times as long as the simple thicker basal part.
Dimensions.—Length of the spines 0.12 to 0.2 of the branches 0.08 to 0.14.
Habitat.—North Atlantic, coast of Norway, Claparède, surface.
2. Plagiacantha furcata, n. sp.
Spines straight, cylindrical, divided into two divergent straight branches of equal size, of about the same length as the simple basal part. The spines and their branches are smooth.
Dimensions.—Length of the spines 0.24, of their fork-branches 0.12.
Habitat.—North Pacific, Station 254, surface.
3. Plagiacantha dodecantha, n. sp.
Spines straight, three-sided prismatic, in the middle with one verticil composed of three divergent straight branches of equal size, of about the same length as the simple basal part. The edges of the spines and their branches are thorny.
Dimensions.—Length of the spines 0.24, of the branches 0.1.
Habitat.—Central Pacific, Station 274, surface.
4. Plagiacantha abietina, Richard Hertwig.
Spines straight, three-sided prismatic, with three verticils of three divergent straight lateral branches, decreasing in size towards the distal end; the branches of the first verticil about twice as long as those of the second, and four times as long as those of the third verticil. All nine branches of each spine simple, straight, three-sided pyramidal.
Dimensions.—Length of the spines 0.2 to 0.3, of the basal branches 0.06 to 0.08.
Habitat.—Mediterranean, Messina (R. Hertwig), surface.
5. Plagiacantha verticillata, n. sp.
Spines curved, three-sided prismatic, with six to nine verticils of three divergent branches, decreasing in size towards the distal end; the branches of the first verticil about twice as long as those of the fourth verticil. All branches simple, slightly curved, bristle-shaped.
Dimensions.—Length of the spines 0.27, of the basal branches 0.12.
Habitat.—South Pacific, Station 296, surface.
