9. Tessaraspis quadriforis, n. sp.
Parmal meshes irregular, roundish, of nearly equal size, four to six times as broad as the bars, and on an average of the same size as the roundish sutural meshes. Radial spines quadrangular, prismatic in the inner part, which is somewhat longer than the conical outer part.
Dimensions.—Diameter of the shell 0.16, of the pores 0.012 to 0.018, bars 0.003.
Habitat.—North Atlantic, Canary and Cape Verde Islands, Station 353, surface.
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.