Subgenus 2. Thecosphærella, Haeckel.
Definition.—Pores of the cortical shell regular, circular, without hexagonal frames or lobes, all of nearly equal size and form.
5. Thecosphæra inermis, Haeckel.
Cortical shell thin walled, rough, with regular circular pores, twice as broad as the bars. Radial proportion of the three spheres and of their circular regular pores = 1 : 2 : 4. All three spheres connected by twelve regularly disposed radial beams.
Dimensions.—Diameter of the outer shell 0.1, middle 0.05, inner 0.025; cortical pores 0.006, bars 0.003.
Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, at many Stations and at various depths.
6. Thecosphæra æquorea, Haeckel.
Cortical shell thick walled, smooth, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres and of their regular pores = 1 : 2 : 6 or = 1 : 3 : 9; they are connected by six radial beams, opposite by pairs in the three dimensive axes.
Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.03 to 0.04, inner 0.09 to 0.12; cortical pores and bars about 0.006.
Habitat.—Mediterranean, Corfu, surface; fossil in Greece and Sicily.
7. Thecosphæra medusa, Haeckel.
Actinomma medusa, Haeckel, 1862, Monogr. d. Radiol., p. 444.
Actinomma medusa, Stöhr, 1880, Palæontogr., Bd. xxvi. p. 90, Taf. ii. fig. 3.Cortical shell thick walled, rough or thorny, with regular circular pores of the same breadth as the bars. Radial proportion of the three spheres = 1 : 2 : 4 (or 1 : 2.5 : 6); they are connected by four radial beams, crossed by pairs in two diameters, perpendicular one to another.
Dimensions.—Diameter of the outer shell 0.08 to 0.12, middle 0.04 to 0.06, inner 0.02 to 0.025; cortical pores and bars in average 0.005.
Habitat.—Fossil in Tertiary rocks of Barbados and the Mediterranean.
