Page:Scientific results HMS Challenger vol 18 part 2.djvu/221

Rh is crossed by horizontal zygomatic bars (between the ascending orbital and the descending maxillary bars). Lateral lattice-girdle narrow, with few large meshes.

Dimensions.—Shell 0.24 long, 0.2 broad; ring 0.09 long.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

5. Amphispyris subquadrata, n. sp. (Pl. 88, fig. 5).

Shell compressed, nearly square, spiny, with slight sternal incision and two distinct transverse strictures. Similar to the preceding species; four pairs of irregular annular pores of nearly equal size. Zygomatic ring complete. Lateral lattice-girdle narrow, with few large meshes.

Dimensions.—Shell 0.14 long, 0.12 broad; ring 0.06 long.

Habitat.—Central Pacific, Station 285, depth 2275 fathoms.

6. Amphispyris costata, n. sp. (Pl. 88, fig. 3).

Shell compressed, nearly square, with slight sternal incision and two obliterated transverse strictures. Similar to the two preceding species; with four pairs of large annular pores, the two middle of which (the orbital and nasal holes) are much larger than the superior (frontal) and inferior (oral) holes. Zygomatic ring incomplete. Lateral lattice-girdle broad, with very numerous, small, irregular, polygonal pores.

Dimensions.—Shell 0.2 long, 0.16 broad; ring 0.07 long.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

7. Amphispyris toxarium, n. sp. (Pl. 88, fig. 7).

Shell inflated, with deep sternal incision and two distinct transverse strictures. Similar to the preceding species, but with deeper constriction and looser lattice-work. Four pairs of large, irregular, annular pores, the central two of which are much larger. Zygomatic ring complete. Lateral girdle broad, with irregular pores of very different size.

Dimensions.—Shell 0.2 long, 0.14 broad; ring 0.09 long.

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

Definition.— without free basal feet, with three distinct joints, separated by two transverse strictures; lattice-work of the shell complete, simple.

The genus Tricolospyris has arisen from the preceding Amphispyris, its ancestral form, by development of lattice-work which completely closes the large open holes remaining on the ventral and dorsal faces of the latter.