Dimensions.—Diameter of the shell 0.25 to 0.3, of the meshes or pores 0.012 to 0.015, bars below 0.001; length of the main spines 0.03, basal breadth 0.007.
Habitat.—Central Pacific, Stations 272 to 274, depth 2350 to 2750 fathoms.
2. Heliosphæra actinota, Haeckel.
Shell very thin walled, about ten times as broad as one mesh. Pores regular, hexagonal, with thread-like bars; six to eight on the radius. Radial spines at the nodal-points of the network, bristle-shaped, scarcely broader than the bars; about twenty main spines as long as the diameter of the shell, and numerous by-spines, only one-third to one-half as long as the former.
Dimensions.—Diameter of the shell 0.2 to 0.25, of the meshes 0.02 to 0.03, bars below 0.001; length of the main spines 0.2 to 0.3.
Habitat.—Mediterranean (Messina), Atlantic (Canaries, Azores), surface.
3. Heliosphæra echinoides, Haeckel.
Shell thin walled, about six times as broad as one mesh. Pores regular, hexagonal, eight times as broad as the bars. Radial spines arising, not from the nodal-points of the network, but from the midst of the bars (very rare disposition!); twenty main spines regularly disposed, as long as the radius, four times as long as the numerous by-spines; all spines bristle-shaped, of the same breadth as the bars.
Dimensions.—Diameter of the shell 0.09, pores 0.015, bars 0.002; length of the main spines 0.04.
Habitat.—Mediterranean (Messina), surface, Haeckel.
4. Heliosphæra elegans, Haeckel.
Shell very thin walled, about ten times as broad as one mesh. Pores regular, hexagonal, with thread-like bars, which are crossed by tangential bars, so that each side of a hexagon exhibits a regular rectangular cross (exactly the same as in Pl. 19, fig. 5). All radial spines bristle-shaped, as thin as the bars, and arising from the nodal-points; twenty main spines as long as the radius, numerous by-spines scarcely one-sixth as long.
Dimensions.—Diameter of the shell 0.26, pores 0.026, bars below 0.001; length of the main spines 0.13.
Habitat.—Mediterranean (Messina), surface, Haeckel.
5. Heliosphæra pectinata, n. sp. (Pl. 26, fig. 9).
Shell thick walled, combed, about fourteen times as broad as one mesh. Pores subregular, circular, with elevated hexagonal frames, three times as broad as the bars. Radial spines very
