Page:Scientific results HMS Challenger vol 18 part 2.djvu/691

Rh 12. Distephanus octogonius, n. sp.

Dictyocha septenaria, Ehrenberg, 1854, Mikrogeol., Taf. xxxvA., Nr. xxi. fig. 8.

Each pileated piece of the skeleton is a truncated eight-sided pyramid, like that of Distephanus octonarius, but differs from it by having eight short erect teeth, which arise from the corners of the upper smaller ring and lie in the same perradial plains as the eight horizontal spines starting from the corners of the lower larger ring. Ehrenberg has figured only an individual abnormality with seven beams instead of eight, taken from the Antarctic ice; but I found the same form frequent in deep-sea soundings from the Antarctic, almost constantly with eight beams, isolated hats with six, seven, or nine beams being intermingled.

Dimensions.—Diameter of the basal ring 0.02, of the apical ring 0.012.

Habitat.—Antarctic Ocean; in smolten "Pancake-Ice," taken by Sir James Clark Ross in lat. 78° 10' S., long. 162° W. (Ehrenberg); Station 156, depth 1975 fathoms.

13. Distephanus diadema, n. sp.

Dictyocha diadema, Haeckel, 1881, Prodromus.

Each pileated piece of the skeleton is an eight-sided pyramid, like that of the two foregoing species, but differing in the number and distribution of the teeth or spines, which are thirty-two. From the eight corners of the basal ring start eight long, nearly horizontal perradial spines, which bear on each side a smaller, nearly vertically descending spine. From the eight corners of the upper ring ascend also eight perradial spines, alternating with the eight interradial beams, which connect the two rings.

Dimensions.—Diameter of the basal ring 0.04, of the apical ring 0.02.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

Definition.— with a skeleton composed of pileated pieces, each of which is a small truncated pyramid with two girdles of meshes (the apical ring being fenestrated).

The genus Cannopilus represents the most highly developed form of Dictyochida. Each piece of the skeleton is a little fenestrated hat or topped pyramid, as in Distephanus. But the apical mesh is simple in the latter, in the former it is divided into several meshes by bars which start in a centripetal direction from the upper ring. Therefore we find two annular rows of meshes, one above the other; an apical or upper row of smaller meshes and a basal or lower row of larger meshes. In the apex of the little