Habitat.—North Pacific, Station 244, surface.
Subfamily Sphærostylida, Haeckel, 1881, Prodromus, pp. 449, 451.
Definition.—Stylosphærida with two concentric, spherical lattice-shells.
Genus 48. Stylosphæra,[[71]] Ehrenberg, 1847, Monatsber. d. Berlin Akad., p. 54.
Definition.—Stylosphærida with two concentric lattice-spheres and two free spines of equal size and similar form.
The genus Stylosphæra, the most simple form of the Sphærostylida, can be derived either from Xiphosphæra by duplication of the spherical shell, or from Carposphæra by development of two opposite polar spines. The inner or medullary shell is enclosed in the central capsule, whilst the outer or cortical shell lies outside it; the two are connected by two or more radial beams, piercing the wall of the capsule.
Subgenus 1. Stylosphærantha, Haeckel.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; surface smooth or a little rough, without spines or thorns.
1. Stylosphæra musa, n. sp.
Radial proportion of the two concentric spheres = 3 : 1. Cortical shell thin walled, smooth, with regular, hexagonal pores, three times as broad as the thin bars; twelve on the half equator. Polar spines three-sided pyramidal, as long as the axis of the cortical shell, one-tenth as broad at the base.