Page:Scientific results HMS Challenger vol 18 part 1.djvu/1052

844 2. Icosaspis elegans, n. sp. (Pl. 136, fig. 4; Pl. 134, fig. 9).

Tessaraspis elegans, Haeckel, 1882, Manuscript et Atlas.

Parmal meshes of very different size and form; in the centre of each plate a cross of four primary, pear-shaped "aspinal pores" (the largest of all); between them four secondary, little smaller, crossed, egg-shaped "angular pores"; around this rosette of eight larger meshes an inner complete circle of sixteen to twenty polygonal coronal pores, and an outer incomplete circle of thirty to forty very small marginal pores. The latter are smaller than the irregular sutural meshes, which are constricted in the middle, about forty to sixty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner. In this elegant and very common species the condyles usually remain separated by sutures; but sometimes the latter become obliterated, and the whole shell then forms a single piece, Icosaspidium elegans.

Dimensions.—Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.02, smaller 0.001 to 0.003; sutural pores 0.005 to 0.015; bars 0.003.

Habitat.—Tropical and Subtropical Atlantic, Canary Islands to Ascension Island, Stations 340 to 354, surface.

3. Icosaspis cruciata, n. sp. (Pl. 134, fig. 10).

Parmal meshes very different; in the centre of each plate a cross of four primary, nearly oblong, rectangular "aspinal pores"; between these four secondary, triangular, egg-shaped "angular pores" (the largest of all), and around this rosette a single circle of twelve to twenty-four small "coronal pores." The latter are of about the same size as the irregular sutural meshes, of which there are twenty to thirty around each plate. Radial spines thin, cylindrical, or a little compressed; their outer part longer than the inner.

Dimensions.—Diameter of the shell 0.2 to 0.3, commonly 0.25; larger parmal pores 0.025, smaller 0.005 to 0.01; bars 0.005.

Habitat.—Tropical and Subtropical Pacific, Sandwich to Marquesas Islands, Stations 256 to 274, surface.

4. Icosaspis ornata, n. sp.

Parmal meshes very different; in the centre of each plate a cross of four primary octagonal aspinal pores (the largest of all); between them four secondary, rhombic angular pores, and around this rosette a circle of twelve to sixteen smaller, polyhedral coronal pores, which are however larger than the irregular sutural pores (surrounding each plate to the number of twenty to thirty). Radial spines thin, quadrangular, prismatic; the outer part longer than the inner.

Dimensions.—Diameter of the shell 0.25; larger parmal pores 0.03, smaller 0.01; sutural pores 0.004 to 0.008; bars 0.006.

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