Page:Scientific results HMS Challenger vol 18 part 2.djvu/601

Rh 3. Dictyomitra conica, n. sp.

Shell widely conical, with six to eight prominent strictures. All joints nearly equal in length, gradually increasing in breadth, the eighth five times as broad as long, and twice as broad as the third. In each joint three to four transverse rows of regular, hexagonal pores. (Similar to Lithostrobus hexagonalis, Pl. 79, fig. 20, but more slender, and without cephalic horn.)

Dimensions.—Length of the shell (with seven joints) 0.16, of each joint 0.022; breadth of the sixth 0.08.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Definition.—Shell smooth, with joints of very different lengths.

4. Dictyomitra polypora, Zittel.

Dictyomitra polypora, Zittel, 1876, Zeitschr. d. deutsch. geol. Gesellsch., p. 80, Taf. ii. fig. 1.

Shell slender, conical, rough, with six to nine deep strictures. Breadth and length of the joints gradually increasing, so that the eighth joint is twice as long and broad as the third. Pores regular, circular, in transverse rows, four rows in each joint, in the last joint five to six rows.

Dimensions.—Length of the shell (with eight joints) 0.24; length of the eighth joint 0.04, breadth 0.1; length of the third joint 0.02, breadth 0.05.

Habitat.—Fossil in secondary rocks of Northern Germany (chalk of Brunswick, &c.), Zittel.

5. Dictyomitra eurythorax, n. sp. (Pl. 77, fig. 4).

Lithocampium eurythorax, Haeckel, 1881, Prodromus, p. 437, et Atlas, pl. lxxvii. fig. 4.

Shell campanulate, conical, rough, with three deep strictures. Cephalis small, hemispherical. Thorax large, inflated, hemispherical, with six transverse rows of pores. Abdomen with two broader joints, together as long as the thorax, each with three to four rows of pores.

Dimensions.—Length of the shell (with four joints) 0.14, of the thorax 0.06; breadth of the thorax 0.08, of the last joint 0.1.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

6. Dictyomitra microcephala, Haeckel.

Eucyrtidium microcephalum, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 32; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, p. 291, Taf. xi. fig. 24.

Shell broadly conical, smooth, with six to eight distinct strictures. Breadth of the joints gradually increasing, length unequal. The three first joints short, only one-half or one-third as long as