Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia) / Report on the Scientific Results of the Voyage of H.M.S. Challenger During the Years 1873-76, Vol. XVIII

by Ernst Haeckel

Arms of equal size and equidistant, club-shaped, three times as long as the diameter of the central disk, which equals the breadth of the thickened distal end; the latter is armed with a strong pyramidal terminal spine. (The diagnosis of Ehrenberg is "Radiis stellæ tribus, apice cuneatis subacutis.")

Dimensions.—Radius of the arms 0.2, basal breadth 0.04, distal breadth 0.07.

Habitat.—North Atlantic, surface and various depths; Greenland; Mexican Gulf Stream; Færöe Channel (John Murray).

4. Rhopalodictyum bifidum, n. sp.

Arms of equal size and equidistant, in the distal half forked, twice as long as the diameter of the central disk; both fork branches half as broad as the simple basal part, truncated at the distal end.

Dimensions.—Radius of the arms 0.16, basal breadth 0.08, distal breadth 0.04.

Habitat.—North Pacific, Station 237, surface.

Subgenus 2. Triactinosphæra, Dunikowski, 1882, Denkschr. d. k. Akad. d.

Definition.—Triangular shell bilateral or irregular, with three arms of different size or distance.

5. Rhopalodictyum zittelii, Haeckel.