1. Cenolarcus primordialis, n. sp. (Pl. 50, figs. 7, 7a, 7b).
Network of the shell regular, with circular, hexagonally framed pores, twice as broad as the elevated bars; about ten pores on the half meridian, eight on the half equator. Surface a little rough. Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Principal axis (or length) 0.12, transverse axis (or breadth) 0.1, sagittal axis (or thickness) 0.08; pores 0.01, bars 0.005.
Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.
2. Cenolarcus dimensivus, n. sp.
Network of the shell regular, with circular pores (without hexagonal frames), three times as broad as the thin bars; about twelve pores on the half meridian, nine on the half equator. Surface thorny. Proportion of the three dimensive axes = 3 : 4 : 5.
Dimensions.—Principal axis 0.15, transverse axis 0.12, sagittal axis 0.09; pores 0.012, bars 0.004.
Habitat.—North Pacific, Station 244, surface.
3. Cenolarcus triaxonius, n. sp.
Network of the shell regular, with circular, hexagonally framed pores, four times as broad as the thin bars; about twelve pores on the half meridian, nine on the equator. Surface smooth. From the inner surface of the shell arise six very thin radial beams, opposite in pairs in the three dimensive axes; all six beams end freely in a little knob, at an equal distance from the centre; therefore this remarkable species seems to have lost a medullary shell (descending from Coccolarcus or Larnacilla?). Proportion of the three dimensive axes = 2 : 2.5 : 3.
Dimensions.—Principal axis 0.13, transverse axis 0.11, sagittal axis 0.09; pores 0.012, bars 0.03.
Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.
4. Cenolarcus lentellipticus, n. sp.
Network of the shell regular, with circular pores of the same breadth as the thick bars; about eighteen pores on the half meridian, fourteen on the half equator. Surface smooth. Proportion of the three dimensive axes = 2 : 3 : 4.
Dimensions.—Principal axis 0.16, transverse axis 0.12, sagittal axis 0.08; pores and bars 0.004.
Habitat.—Western Tropical Pacific, Station 224, surface.
5. Cenolarcus minimus, n. sp.
Network of the shell subregular, with very small circular pores of the same breadth as the bars; only four pores on the half meridian, three on the half equator. Surface smooth. Proportion of the three dimensive axes = 3 : 4 : 5.
