Page:Scientific results HMS Challenger vol 18 part 2.djvu/683

Rh 1. Dictyocha navicula, Ehrenberg.

Dictyocha navicula, Ehrenberg, 1838, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 129; Mikrogeol., Taf. xx., Nr. i. fig. 43.

Dictyocha ponticulus, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 267.

Each individual ring elliptical or oblong, with one transverse arch in the shorter axis, which bisects it into two meshes. No spines or teeth.

Dimensions.—Diameter of the ring 0.02, of the bars 0.001.

Habitat.—Fossil in Tertiary deposits, Barbados, Sicily, &c.; living in the Atlantic, Stations 352, 354, and off Bermuda, surface.

2. Dictyocha quadrata, Ehrenberg.

Dictyocha quadrata, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 267.

Each individual ring square or rhomboid, with one transverse arch in the shorter axis, forming two meshes. Two peripheral opposite spines on the poles of one axis.

Dimensions.—Diameter of the ring 0.015.

Habitat.—Atlantic, Bermuda Islands; fossil in Barbados.

3. Dictyocha pons, Ehrenberg.

Dictyocha pons, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., Taf. xxi. fig. 40.

Dictyocha tripyla, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80; Mikrogeol., Taf. xxi. fig. 41.

Each individual ring elliptical or oblong, with one transverse arch in the shorter axis, forming two meshes. Four peripheral spines, on the poles of the longer and of the shorter axis. (The individual abnormality, figured as Dictyocha tripyla, loc. cit., Taf. xxi. fig. 41, has the transverse arch bifid at one end, therefore three meshes result; this forms an interesting transition to Dictyocha fibula.)

Dimensions.—Diameter of the ring 0.01, of the bars 0.001.

Habitat.—Fossil in Tertiary rocks, Oran, Africa.

4. Dictyocha triommata, Ehrenberg.

Dictyocha triommata, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 76; Mikrogeol., Taf. xxxiii., Nr. xv. fig. 11.

Dictyocha triactis (= triacantha), Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 80.

Dictyocha trifenestrata, Ehrenberg, 1841, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 410; Mikrogeol., Taf. xix. fig. 38.

Dictyocha abyssorum, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 38.

Each pileated piece of the skeleton is a small three-sided pyramid, the sides of which form three triangular meshes; the three edges between them are three curved interradial beams, united in the