Habitat.—South Pacific, Station 300, depth 1375 fathoms.
Subgenus 6. Circoniscus, Haeckel.
Definition.—Ring with seven or more chambers, separated by seven or more radial beams.
12. Archidiscus octoniscus, n. sp.
Ring circular or regular octagonal, connected with the central chamber by eight equidistant radial beams; therefore eight ring chambers of equal size. (Compare the central part of the disk of Porodiscus quadrigatus, Pl. [41], fig. 3.)
Dimensions.—Diameter of the ring 0.04, of the central chamber 0.014.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
13. Archidiscus polythalamus, n. sp.
Ring circular, connected with the central chamber by nine to ten or more radial beams at nearly equal distances. Ring chambers nine to ten, more or less equal, sometimes also eleven to twelve, more different. (This species is very variable, and may perhaps be divided into a number of different "transformistic species.")
Dimensions.—Diameter of the ring 0.04 to 0.06, of the central chamber 0.015.