8. Amphitholus panicium, n. sp. (Pl. [10], fig. 4).
Central chamber ellipsoidal, nearly twice as broad, but of the same height, as both cupolas. Whole surface thorny; the largest radial thorns about as long as the medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. On the base of each cupola a circle of ten to twelve larger square pores, separated by radial beams, which are prolonged into stouter free spines. This remarkable formation of the cupolas, very rare in this family, recalls the characteristic formation of the distal chambers of the Panartida and Zygartida (e.g., Pl. [40], figs. 4, 8, &c.), where it is very common.
Dimensions.—Major axis of the shell 0.15, minor 0.1; pores 0.005 to 0.012, bars 0.003; large square pores 0.02; axes of the medullary shell 0.03 and 0.02.
Habitat.—Indian Ocean, Madagascar, Rabbe, surface.
Genus 292. Amphitholonium,[[331]] n. gen.
Definition.—Tholonida with double cortical shell (with external veil), with two hemispherical cupolas, opposite on the poles of one axis; central chamber (between them) Larnacilla-shaped, with medullary shell.
The genus Amphitholonium differs from the nearly allied Amphitholus (probably its ancestral form) only in the duplication of the cortical shell; the outer has the same three-jointed form as the inner, and is connected with it by a variable number of radial beams. From the similar Tholodes it differs in the possession of a medullary shell.
1. Amphitholonium tricolonium, n. sp. (Pl. [10], fig. 7).
Outer cortical shell smooth, of the same three-jointed form as the inner, at an equal distance from it throughout the whole circumference; central chamber higher-vaulted than both cupolas. Network of the outer shell delicate, with subregular, circular pores. Pores of the thick-walled inner shell subregular, circular, with hexagonal frames, three times as broad as the bars; eight to ten in the basal semicircle of one cupola.
Dimensions.—Major axis of the outer cortical shell 0.2, minor axis 0.15; major axis of the inner cortical shell 0.16, minor axis 0.11; pores 0.01, bars 0.0035.