11. Archicircus hertwigii, Haeckel.
Lithocircus annularis, R. Hertwig (non J. Müller), 1879, Organismus der Radiol., p. 69. Taf. vii. fig. 5.
Gate hexagonal, with prolonged main axis. Ring hexagonal, with two prominent edges and six pairs of equal, short, conical spines, arising from the two edges of the six rods at the six corners and divergent on each side of the plane of the ring. The basal spine-pair is doubled, therefore there are in all fourteen spines.
Dimensions.—Diameter of the gate 0.05 to 0.07; thickness of the ring 0.005 to 0.006.
Habitat.—Mediterranean (Messina), Hertwig, surface.
12. Archicircus triglyphus, n. sp.
Gate ovate. Ring hexagonal, with three prominent edges and twenty-two to twenty-four simple curved spines, arising from the six corners and about as long as the diameter of the gate. In the basal corner arise six to nine larger spines, protecting the basal pole of the central capsule. From each of the five other corners arise three spines, diverging from the three edges.
Dimensions.—Diameter of the gate 0.07 to 0.11; thickness of the ring 0.008 to 0.011.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
13. Archicircus sexangularis, n. sp. (Pl. [81], fig. 12).