3. Trigonactura trigonobrachia, n. sp.
Phacoid shell two and a half times as broad as the medullary shell, with six pores on its radius, without a perfect chambered girdle. Arms nearly equilateral triangular, twice as long as the diameter of the phacoid shell, at the truncated distal end as broad as its diameter and three times as broad as at the narrow base. (Resembles Hymenactura hexagona, but without a patagium.)
Dimensions.—Diameter of the phacoid shell 0.11, of the medullary shell 0.045; length of the arms 0.2, basal breadth 0.035, distal breadth 0.1.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
4. Trigonactura lanceolata, n. sp.
Phacoid shell three times as broad as the medullary shell, with eight pores on its radius, surrounded by one perfect chambered ring. Arms lanceolate, three times as long as the diameter of the phacoid shell, and four times as long as broad in the middle part, at both ends very narrow, blunt.
Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.25, breadth in the midst 0.06.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
Subgenus 2. Trigonactinium, Haeckel.
Definition.—Distal end of the arms armed with a radial spine.
5. Trigonactura triacantha, n. sp. (Pl. 38, figs. 6, 7).
Phacoid shell two and a half times as broad as the medullary shell, with eight pores on its radius, surrounded by one perfect chambered ring. Arms nearly lanceolate, in the middle part one and a half times as broad as at both ends, twice as long as the phacoid shell, at the distal end with a strong pyramidal terminal spine. Through the spongy framework of each arm shine sixteen to eighteen transverse bars (as septa of the joints) and six to eight longitudinal piercing beams.
Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.038; length of the arms 0.2, greatest breadth 0.08.
Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.
6. Trigonactura trigonodiscus, n. sp.
Phacoid shell triangular, twice as broad as the spherical medullary shell, with six to seven pores on its radius, surrounded by one chambered ring. Arms equilateral triangular, as long as
