16. Stylosphæra erato, n. sp.
Radial proportion of the two shells = 3 : 1. Cortical shell thick walled, thorny, with irregular, roundish pores, two to five times as broad as the bars; fourteen to eighteen on the half equator. Polar spines three-sided pyramidal, about as long as the axis of the outer sphere, one-fourth as broad as its radius. (Similar to Xiphosphæra vesta, Pl. [14], fig. 6.)
Dimensions.—Diameter of the outer shell 0.15, pores 0.008 to 0.015, bars 0.003; inner shell 0.05; polar spines 0.12 long, 0.02 broad.
Habitat.—South Atlantic, Station 335, depth 1425 fathoms.
Genus 49. Sphærostylus,[[72]] Haeckel, 1881, Prodromus, p. 451.
Definition.—Stylosphærida with two concentric lattice-spheres and two free spines, of different size or form.
The genus Sphærostylus differs from Stylosphæra in the different size or form of the two polar spines, and therefore has the same relation to it that Xiphostylus bears to Xiphosphæra.
Subgenus 1. Sphærostylantha, Haeckel.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form; surface smooth or a little rough, without thorns.
1. Sphærostylus liostylus, Haeckel.