12. Myelastrum giganteum, n. sp.
Anterior arms somewhat broader and shorter than the posterior. Each arm four-lobed, with three shallow terminal incisions, the middle incision twice as deep as the two laterals. Sagittal constriction a little larger than the transverse. Margin ciliated, with radial bristle-shaped spines as prolongations of the inner radial beams, proceeding from the central disk (as in Myelastrum dodecaceros, Pl. [47], figs. 11, 11a).
Dimensions.—Radius of the anterior arms 0.6, of the posterior 0.8; longitudinal constriction 0.6, transverse 0.5.
Habitat.—Pacific, central area, Station 271, surface.
13. Myelastrum anomalum, n. sp. (Pl. [47], fig. 9).
All four arms of different size and form; anterior arms broader, posterior longer; one anterior arm trifid, the three other arms bifid; length of the branches unequal; all four angles between the arms unequal. (This anomalous form, seen only once, may be an individual abnormality.)
Dimensions.—Radius of the arms 0.4 to 0.7; constrictions 0.3.
Habitat.—North Pacific, Station 237, surface.
Genus 240. Pentalastrum,[[279]] Haeckel, 1881, Prodromus, p. 461.
Definition.—Porodiscida with five simple, undivided, chambered arms, without a patagium.