Dimensions.—Diameter of the shell 0.2, of the pores 0.012.
Habitat.—North Pacific, Station 244, surface.
Subfamily 2. Tessaraspida, Haeckel.
Definition.—Dorataspida with twenty radial spines, each of which bears four crossed apophyses (opposite in pairs). The spherical shell is composed either of the meeting branches of these apophyses (Stauraspida), or of twenty perforated plates, produced by concrescence of their branches (Lychnaspida).
A. Tribe II. Stauraspida, Haeckel, 1881, Prodromus, p. 467.
Definition.—Dorataspida with spherical shell, which is composed either of the meeting branches of the four crossed apophyses only, or exhibits four to twelve perforated plates which are produced by the crossed apophyses of four to twelve radial spines (but never of all twenty spines). Each plate bears four crossed pores.
Genus 358. Stauraspis,[[398]] Haeckel, 1881, Prodromus, p. 467.
Definition.—Dorataspida without perforated plates; shell composed only of the meeting branches of the four crossed apophyses, which arise (opposite in pairs) from each radial spine. Condyles of the branch-ends without by-spines.
The genus Stauraspis is the most simple and primitive form among all Tessaraspida, or that subfamily of Dorataspida, in which the shell is composed of twenty radial spines, each of which bears four crossed apophyses. The subfamily may be divided into two different tribes, the Stauraspida and Lychnaspida. In the Stauraspida either all twenty spines, or a part of them, bear no perforated plates, and the shell is composed wholly or partially of the meeting branches of their apophyses. In the Lychnaspida, however, the four apophyses of each single spine form, by reunion of their recurved branches, a plate or shield with four crossed aspinal pores. The Lychnaspida represent therefore a more developed stage in the shell-formation than the simpler Stauraspida. Stauraspis, as the common ancestral form of both, may be derived phylogenetically from Xiphacantha or Stauracantha, which differ only by the apophyses or branches of the apophyses not meeting. These branches (originally eight on each spine) are either simple or again branched.