Habitat.—Central Pacific, Station 268, depth 2900 fathoms.
17. Actinomma giganteum, n. sp.
Cortical shell thick walled, little larger than the outer medullary shell, whilst the inner is only one-tenth as large. Pores of all three shells irregular, roundish, or subcircular, twice to three times as broad as the bars, on an average twice as large in the outer and middle as in the inner shell. Sixty to eighty short conical radial spines on the surface, about as long as the diameter of the inner shell, and one-fourth as broad at the base. Radial proportion of the three spheres = 1 : 9 : 10.
Dimensions.—Diameter of the outer shell 0.4 to 0.5, middle 0.35 to 0.45, inner 0.05 to 0.06.
Habitat.—Fossil in Barbados.
Genus 102. Echinomma,[[138]] Haeckel, 1881, Prodromus, p. 453.
Definition.—Astrosphærida with three concentric lattice-spheres and numerous simple radial spines of two different kinds; larger main spines and smaller by-spines.
The genus Echinomma, differs from its ancestral form, Actinomma, in the differentiation of the radial spines. Whilst a large number of small by-spines cover the entire surface, a smaller number of large main spines are scattered over it, or limited to certain regularly distributed points. It represents Heliosoma among the Haliommida.
Subgenus 1. Echinommetta, Haeckel.
Definition.—Pores of the cortical shell regular, of nearly equal size and similar form.