Page:Scientific results HMS Challenger vol 18 part 2.djvu/824

1700 sometimes six) ovate, basal pores (fig. 3b). Mouth armed with a corona of eight short, conical, vertical, spinulate teeth (fig. 3a).

Dimensions.—Diameter of the shell 0.4 to 0.5, length of the spines 0.2 to 0.25.

Habitat.—South-Eastern Pacific (off Valparaiso), Station 298, depth 2225 fathoms.

2. Circostephanus sexagenarius, n. sp.

Shell polyhedral, with sixty triangular, equilateral congruent faces which are nearly plane, and separated by high prominent crests. They are disposed in twelve pentagonal groups, each with five faces, so that they appear as if derived from a regular pentagonal dodecahedron, the twelve regular faces of which are each divided into five congruent triangles, meeting in its centre. From the elevated corners of the polyhedron arise thirty-two radial spines (twelve in the central points of the pentagons, twenty in the meeting corners of every three pentagons). The radial spines are nearly as long as the diameter of the shell, cylindrical, spinulate, and surrounded at the distal end by a verticil of five stout, curved branches, and at the pyramidal base by a corona of twelve to sixteen basal pores. Mouth armed with a corona of twelve conical, vertical, spinulate teeth.

Dimensions.—Diameter of the shell 0.75, length of the spines 0.6.

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

3. Circostephanus polygonarius, n. sp.

Shell polyhedral, with sixty to eighty subregular, triangular, concave faces, which are separated by prominent crests. From the elevated corners of the polyhedron arise thirty to forty radial spines, which are longer than the diameter of the shell, densely covered with curved bristles and three-sided prismatic, with three spirally convoluted edges. Their distal end is surrounded by a verticil of eight or nine curved branches, and their pyramidal base by a corona of eight or nine basal pores. Mouth armed with a corona of ten conical, vertical, spinulate teeth.

Dimensions.—Diameter of the shell 0.8, length of the spines 0.9.

Habitat.—South Pacific, Station 288, depth 2600 fathoms.

Definition.— with dimpled spherical shell, not composed of polygonal plates. The shell is covered with small roundish dimples, never polyhedral, and the radial spines are simple, not branched, and usually not regularly arranged.

Definition.— with spherical shell of a peculiar dimpled, porcellanous structure, and with a variable number of simple radial main-spines which are usually not regularly arranged.