Subgenus 1. Prunuletta, Haeckel.
Definition.—Network of the cortical shell regular, with meshes of equal size and similar form.
1. Prunulum frugulum, n. sp.
Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the bars; ten to twelve on the half equator. Proportion of the major axis of the ellipsoid to the minor = 4 : 3. Both medullary shells spherical. (Differs from Druppula drupa almost entirely in the double medullary shell.)
Dimensions.—Major axis of the ellipsoidal cortical shell 0.12, minor 0.09; pores 0.006, bars 0.002; diameter of both medullary shells 0.05 and 0.03.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.
2. Prunulum cerasum, n. sp.
Cortical shell thick walled, smooth, with circular, hexagonally framed pores, of the same breadth as the bars; sixteen to eighteen on the half equator. Proportion of the two axes of the ellipsoid = 5 : 4. Both medullary shells spherical. (The cortical shell resembles that of Pipetta tuba, Pl. 39, fig. 7, without the polar tubes.)
Dimensions.—Major axis 0.15, minor 0.12; pores and bars 0.007; diameter of the medullary shells 0.08 and 0.04.
Habitat.—South Atlantic, Station 332, depth 2200 fathoms.
3. Prunulum amygdalum, n. sp.
Cortical shell thick walled, smooth, with regular, circular, hexagonally lobulated pores, three times as broad as the bars; twelve to fourteen on the half equator (of the same form as in Druppula phœnix and in Stauroxiphos gladius, Pl. 15, fig. 7). Proportion of the two axes = 6 : 5. Inner medullary shell spherical, outer ellipsoidal.
Dimensions.—Major axis 0.12, minor 0.1; pores 0.009, bars 0.003; diameter of the medullary shells 0.07 and 0.04.
Habitat.—Mediterranean (Corfu), surface.
4. Prunulum coccymelium (Pl. 39, fig. 4).
Cortical shell thin walled, slightly rough, with regular, circular pores, twice as broad as the bars; twelve to fifteen on the half equator. Proportion of both axes = 4 : 3. Both medullary shells spherical.
Dimensions.—Major axis 0.12, minor 0.09; pores 0.006, bars 0.003; diameter of the medullary shells 0.06 and 0.03.
Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.
