All rings of the disk concentric, circular, of equal breadth. Pores irregular, roundish, one and a half to two on the breadth of each ring. Margin of the disk thorny, of the same thickness as the central part of the medal-shaped or cylindrical disk. Two opposite radial spines very long and thin, cylindrical, twice to three times as long as the diameter of the disk, only half as thick as the breadth of one ring.
Dimensions.—Diameter of the disk (with five rings) 0.17; breadth of each ring 0.014; pores 0.003 to 0.012.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
2. Xiphodictya amphirrhopalia, n. sp. (Pl. [42], fig. 11).
All rings of the disk concentric, circular, with increasing breadth from the centre; the fifth ring twice as broad as the second. Central chamber very large. Margin of the lenticular disk thorny, much thinner than the central part. Pores irregular, roundish, two to three on the breadth of each ring. Two opposite radial spines club-shaped, about as long as the diameter of the disk, in the outer spindle-shaped part three to four times as broad as at the base.
Dimensions.—Diameter of the disk (with six rings) 0.17; breadth of the second ring 0.008, of the fifth ring 0.016.
Habitat.—Pacific, central area, Station 265, depth 2900 fathoms; also fossil in the Tertiary rocks of Sicily (Caltanisetta).
Subgenus 2. Xiphospira, Haeckel.
Definition.—All rings of the disk or a part of them not concentric, spirally convoluted; sometimes irregular or interrupted.
3. Xiphodictya staurospira, n. sp. (Pl. [42], fig. 12).