Definition.—Liosphærida with three concentric spherical lattice-shells, which are united by radial beams.
Genus 21. Thecosphæra,[[34]] Haeckel, 1881, Prodromus, p. 452.
Definition.—Liosphærida with two medullary (intracapsular) shells and one cortical (extracapsular) shell.
The genus Thecosphæra comprises a large number of triple-shelled Sphæroidea, formerly united with Actinomma, but different from this genus in the absence of radial spines. The latticed shell is composed of three concentric spheres, two of which lie within the central capsule (medullary shells), and one outside (cortical shell). This latter is connected with the former by radial beams piercing the wall of the central capsule. From the following Rhodosphæra (with one medullary and two cortical shells) Carposphæra differs also by the distance of the three shells. In the former the distance between the two outer shells is much smaller, in the latter much larger, than the distance between the inner shells.
Subgenus 1. Thecosphærantha, Haeckel.
Definition.—Pores of the cortical shell regular, hexagonal, or circular, with hexagonal frames or lobes, all of nearly equal size and form.
1. Thecosphæra triplodictyon, n. sp.
Cortical shell thin walled, smooth, with regular, hexagonal pores, four times as broad as the bars. Radial proportion of the three spheres = 1 : 2 : 8. Both medullary shells with regular circular pores, twice as broad as the bars, the inner half as broad as the outer. All three shells connected by six thin radial beams, opposite in pairs in the three dimensive axes.
Dimensions.—Diameter of the outer shell 0.2, middle 0.05, inner 0.025; cortical pores 0.012, bars 0.003.
Habitat.—Central Pacific, Station 271, surface.