Page:Scientific results HMS Challenger vol 18 part 2.djvu/449

Rh 2. Dictyoceras formica, n. sp. (Pl. 71, fig. 8).

Shell with obliterate collar, but deep lumbar stricture. Length of the three joints = 1 : 2 : 3, breadth = 2 : 5 : 4. Cephalis conical, with an oblique curved horn of the same length. Thorax with three vaulted swellings between the three prominent, diverging lattice-wings, the apex of which is prolonged downwards into a solid curved spine, half as long as the inflated abdomen. Mouth little constricted. Pores irregular, roundish, of different sizes.

Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.06; breadth, a 0.03, b 0.1, c 0.09.

Habitat.—North Atlantic, Station 353, surface.

3. Dictyoceras melitta, n. sp. (Pl. 71, fig. 9).

Shell with two deep strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 6 : 5. Cephalis subspherical, with two conical divergent horns of the same length. Thorax three-sided pyramidal, the three edges prolonged into three lattice-wings of the same form, with short, terminal spines. Abdomen inflated, subovate, with constricted mouth. Pores small, regular, circular, of equal size, with very thin bars.

Dimensions.—Length of the three joints, a 0.03, b 0.09, c 0.12; breadth, a 0.04, b 0.18, c 0.15.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.

4. Dictyoceras bombus, n. sp. (Pl. 71, fig. 10).

Shell with deep collar, but evanescent lumbar stricture. Length of the three joints = 1 : 5 : 3, breadth = 1 : 6 : 7. Cephalis subspherical, with a conical horn of the same length. Thorax campanulate, with three short and broad, triangular lattice-wings, the upper edge of which is nearly horizontal, the lower nearly vertical and decurrent from the height of the collar to the lumbar stricture. Abdomen inflated, with constricted mouth of half the breadth. Pores small, subregular, circular, of nearly equal size.

Dimensions.—Length of the three joints, a 0.02, b 0.1, c 0.06; breadth, a 0.025, b 0.12, c 0.14.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

5. Dictyoceras virchowii, Haeckel.

Dictyoceras virchowii, Haeckel, 1862, Monogr. d. Radiol., p. 333, Taf. viii. figs. 1-5.

Lithornithium dictyoceras, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1860, p. 840.

Shell with two distinct strictures. Length of the three joints = 1 : 3 : 4, breadth = 1 : 5 : 6. Cephalis subspherical, with an oblique curved horn of the same length. Thorax conical, with three broad, triangular lattice-wings different in size and direction, two of which are directed outwards, the third downwards—each terminated by a strong spine. Abdomen oblique, inflated, with wide open, truncate mouth. On the shell surface some few conical spines are scattered. Pores irregular,