Page:Scientific results HMS Challenger vol 18 part 2.djvu/685

8. Dictyocha fibula, Ehrenberg.

Dictyocha fibula, Ehrenberg, 1839, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 149; Mikrogeol., Taf. xviii. fig. 54, a, b, c, Taf. xix. fig. 43, Taf. xx. fig. 45, Taf. xxi. fig. 42, &c.

Dictyocha abnormis, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76; Mikrogeol., 1854, Taf. xxxvA., Nr. xvii. fig. 9.

Dictyocha bipartita, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 44.

Dictyocha tenella, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. ii. fig. 11.

Each pileated piece of the skeleton stirrup-shaped, with two pairs of meshes, and a square basal ring, the four corners of which are prolonged into four perradial spines. Between the latter four interradial beams arise from the sides in pairs, and the two pairs are connected by a diagonal arch. Therefore the two opposite meshes are larger and pentagonal, the other two meshes (alternating with these) are smaller and square. No vertical spine on the apex.

Dimensions.—Diameter of the basal square ring (diagonal) 0.01 to 0.02, of the meshes 0.005.

Habitat.—Fossil in different Tertiary rocks (Barbados, Oran, Greece, Sicily, &c.), Ehrenberg.

9. Dictyocha messanensis, Haeckel.

Dictyocha messanensis, Haeckel, 1862, Monogr. d. Radiol., p. 272, Taf. xii. figs. 3-6. Dictyocha fibula, R. Hertwig (not Ehrenberg), 1879, Organismus d. Radiol., p. 89, Taf. ix. fig. 5.

Each pileated piece of the skeleton stirrup-shaped, very similar to Dictyocha fibula, but distinguished by a vertical apical spine in the centre of the transverse arch, which connects the two pairs of ascending bars.

Dimensions.—Diameter of the basal ring 0.02 to 0.03, of the meshes 0.01 to 0.016.

Habitat.—Mediterranean (Messina), North Atlantic (Canary Islands), Station 354, surface.

10. Dictyocha epiodon, Ehrenberg.

Dictyocha epiodon, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 79; Mikrogeol., Taf. xviii. fig. 55.

Each pileated piece of the skeleton stirrup-shaped, with four paired meshes similar to the hats of Dictyocha fibula, but distinguished by four small centripetal thorns, which start from the inside of the basal ring, at the side of the four ascending beams. No apical spine.

Dimensions.—Diameter of the basal ring 0.03, of the meshes 0.01.

Habitat.—Fossil in Tertiary rocks of North America (Miocene Tripel of Richmond, Virginia, &c.).

11. Dictyocha stapedia, n. sp. (Pl. 101, figs. 10-12).

Each pileated piece of the skeleton stirrup-shaped, with four paired meshes, similar to the hats of Dictyocha fibula and Dictyocha messanensis, but distinguished by four small centripetal teeth, which start from the inside of the basal ring, at the side of the four ascending beams. In the centre of the diagonal arch arises a vertical apical spine (differing from Dictyocha epiodon). This species seems