10. Tessaraspis irregularis, n. sp.
Parmal meshes irregular, roundish, of unequal size, three to six times as broad as the bars, and on an average larger than the irregular sutural meshes. Radial spines cylindrical, the outer part longer than the inner part.
Dimensions.—Diameter of the shell 0.13, parmal pores 0.006 to 0.012, sutural pores 0.005 to 0.01; bars 0.002.
Habitat.—Central Pacific, Station 270, surface.
Subgenus 2. Tessaraspidium, Haeckel.
Definition.—Condyles of the neighbouring plates grown together and sutures obliterated; therefore the whole shell forms a single piece of acanthin.
11. Tessaraspis quadrata, n. sp.
Parmal meshes square, four times as broad as the thin bars, on an average of the same size as the polygonal sutural meshes. Radial spines stout, tetrapterous, prismatic, in the outer part longer than in the inner. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.
Dimensions.—Diameter of the shell 0.16, of the parmal pores 0.012, sutural pores 0.01 to 0.015.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
12. Tessaraspis rotunda, n. sp.
Parmal meshes circular, of equal size, twice as broad as the thick bars, on an average smaller than the roundish sutural meshes. Radial spines cylindrical in the inner part, which is somewhat longer than the outer conical part. Sutures of the shell completely obliterated, therefore the whole shell forms one piece.
Dimensions.—Diameter of the shell 0.12, parmal pores 0.008, sutural pores 0.005 to 0.015.
Habitat.—North Atlantic, Station 354, surface.
13. Tessaraspis concreta, n. sp. (Pl. 136 fig. 5).
Parmal meshes irregular, polygonal or roundish, six to eight times as broad as the narrow and high bars, much larger than the irregular sutural meshes. Radial spines leaf-shaped, compressed, two-edged, pointed at both ends; inner and outer part nearly of equal size. Shell very thick walled; meshes therefore funnel-shaped; sutures completely obliterated, therefore the whole shell forms a single piece.
Dimensions.—Diameter of the shell 0.09, parmal pores 0.02, sutural pores 0.01.
Habitat.—Central Pacific, Station 274, depth 2750 fathoms.
