Definition.—Shell with fifty-four sutures; four polar plates on each pole of the main axis different in pairs; two major hexagonal meeting in a polar suture (the "hydrotomical suture"); two minor pentagonal, not meeting together (separated by that hydrotomical suture). Spherical shell therefore composed of eight hexagonal plates (four equatorial and four polar) and by twelve pentagonal plates (eight tropical and four polar plates).
4. Dorataspis loricata, Haeckel.
Dorataspis loricata, Haeckel, 1862, Monogr. d. Radiol., p. 415, Taf. xxi. figs. 3-6.
Shell with fifty-four sutures and fifty-four sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate kidney-shaped or roundish, nearly of the same size as the sutural meshes. Radial spines cylindrical; their outer half on the pointed distal end two-edged and longer than the inner half.
Dimensions.—Diameter of the shell 0.14, of its meshes 0.008 to 0.016.
Habitat.—Mediterranean (Messina), North Atlantic (Canary Islands), Azores, surface.
5. Dorataspis typica, n. sp. (Pl. [138], figs. 4, 4a).
Shell with fifty-four crest-like sutures and fifty-four circular sutural meshes, with eight hexagonal and twelve pentagonal plates. Both aspinal meshes of each plate elliptical, twice to three times as broad as the sutural meshes. Aspinal meshes of the four equatorial plates twice as broad as those of the sixteen other plates. The meshes are surrounded by elevated and denticulated crests (incipient spine-sheaths). Radial spines compressed, more or less two-edged; outer pointed half somewhat larger than the inner half. (In this typical species the composition of the shell prevailing in the majority of Ceriaspida is very clear.)
Dimensions.—Diameter of the shell 0.15 to 0.18, of the aspinal pores 0.02 to 0.03, of the sutural pores 0.01.
Habitat.—Central Pacific, Stations 270 to 274, surface and in various depths.