Page:Scientific results HMS Challenger vol 18 part 2.djvu/605

Rh regularly disposed in longitudinal series, alternate, with prominent ribs. The upper conical part of the shell is about half as long as the lower cylindrical part. Cephalis with a large, pyramidal horn of three times the length. Dedicated to Johannes Müller (Berlin, 1858).

Dimensions.—Length of the shell (with ten joints) 0.22; breadth of the third joint 0.09, of the fourth joint 0.06.

Habitat.—Central Pacific, Station 268, depth 2900 fathoms.

Definition.— (vel Stichocyrtida eradiata aperta) with cylindrical shell, the upper pole of which is rounded, the lower truncate. Cephalis with a horn.

The genus Artostrobus and the following Dictyomitra differ from all the other Stichocorida in the cylindrical or nearly cylindrical form of the shell, all the joints of which are nearly equal in breadth, and are very short, often with a single transverse row of pores only. The first joint or cephalis is usually different from the following, often hemispherical or cap-shaped joints. The last joint is truncate, and has a wide open mouth. Since the constrictions between the single joints are often very slight, some species are very similar to the Dicyrtide Sethocorys.

Definition.—A single transverse row of small, circular pores on each joint. (Sometimes on the uppermost joints two or three rows.)

1. Artostrobus annulatus, Haeckel.

Cornutella annulata, Bailey, 1856, Amer. Journ. Sci. and Arts, vol. xxii. pl. i. fig. 5a, 5b.

Eucyrtidium annulatum, Haeckel, 1862, Monogr. d. Radiol., p. 327.

Shell slender, cylindrical, smooth, without external strictures, but with ten to twenty internal annular septa. On each joint only a single transverse row of small pores. Cephalis hemispherical, with a single or double small horn. Each joint about four times as broad as long.

Dimensions.—Length of the shell (with twenty joints) 0.2; length of each joint 0.01, breadth 0.04.

Habitat.—Arctic Ocean, Kamtschatka (Bailey); Greenland (Ehrenberg).