6. Zygocircus hexagonus, n. sp.
Gate irregularly hexagonal. Ring obliquely hexagonal, thick, without edges, with six short and stout conical spines on the six corners. The two spines of the curved ventral rod are longer than the two spines of the straight dorsal rod. The apical spine is smaller and the basal spine larger than the four others.
Dimensions.—Diameter of the gate 0.07 to 0.09; length of the spines 0.01 to 0.03.
Habitat.—North Pacific, Station 241, depth 2300 fathoms.
7. Zygocircus triquetrus, n. sp. (Pl. 81, fig. 3).
Gate obliquely ovate. Ring obliquely hexagonal, with three sharp edges and three short conical spines on each of the six corners. Therefore each hexagonal edge bears six short radial spines of equal size.
Dimensions.—Diameter of the gate 0.04 to 0.08; length of the spines 0.01 to 0.02.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.
8. Zygocircus dodecanthus, n. sp.
Gate semicircular. Ring semicircular or irregularly hexagonal, without edges, with twelve short blunt spines, arising in pairs from the six corners; two apical, two basal, and between them two equatorial corners. Three pairs of spines remain on the straight dorsal rod, three on the curved ventral rod.
Dimensions.—Diameter of the gate 0.04 to 0.06; length of the spines 0.01 to 0.02.
Habitat.—Central Pacific, Stations 263 to 268; depth 2650 to 2900 fathoms.
9. Zygocircus acacia, n. sp. (Pl. 81, fig. 5).
Gate obliquely ovate. Ring semi-ovate, with straight dorsal and curved ventral rod, partly with distorted edges. Six bunches of numerous short and straight conical spines arise from the ring, one larger bunch (often trifid) from the apex, two smaller bunches from the dorsal, two from the ventral rod, and one very large bunch from the base. The six bunches are often more separated, smaller, and the spines shorter than in the figured specimen, which passes over into Dendrocircus.
Dimensions.—Diameter of the gate 0.12 to 0.16; length of the spines, 0.01 to 0.07.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
10. Zygocircus polygonus, n. sp. (Pl. 81, fig. 2).
Gate irregularly roundish or ovate. Ring irregularly polygonal or sometimes nearly circular, without edges, armed with a single series of ten to fifteen short pyramidal spines, which are irregularly
