Definition.—Quadrilonchida with two opposite branched (but not latticed) apophyses, either on each radial spine or only on a part of the twenty spines.
The genus Xiphoptera differs from the preceding ancestral genus Quadrilonche in the ramification of the apophyses, which bear perpendicular branches on their distal side. These are therefore parallel to the spine itself. If the branches become united by transverse beams then we get Lithoptera.
1. Xiphoptera tessaractena, n. sp.
Four equatorial spines in the outer third crossed by two opposite transverse apophyses, each of which bears on its distal side two to three branches, perpendicular to the apophysis and parallel to the spine itself. Sixteen other spines much smaller, in the outer third crossed by two simple opposite transverse apophyses.
Dimensions.—Length of the four major spines 0.18, of the sixteen minor 0.05 to 0.1.
Habitat.—North Pacific, Station 238, surface.
2. Xiphoptera dodecactena, n. sp. (Pl. [131], fig. 3).
Four equatorial spines one and a half times to twice as long and broad as the eight tropical spines. These twelve spines have the same form and are crossed in their distal third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches, perpendicular to the apophysis and parallel to the spine. Eight polar spines much smaller than the twelve others, simple, without apophyses. The central capsule of this species exhibited a conical protuberance around the base of each individual spine.
Dimensions.—Length of the twelve larger spines 0.1 to 0.2, of the eight smaller 0.02 to 0.06.
Habitat.—Central Pacific, Station 272, surface.