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, 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.

Subgenus 1. Staurasparium, Haeckel.

Definition.—Apophyses of the spines simple, not branched; therefore each spine with four sutural condyles.

1. Stauraspis cruciata, n. sp. (Pl. , fig. 5).

Radial spines thin, quadrangular, prismatic; outer and inner half nearly of equal length. Central bases pyramidal, with wing-like edges. Four apophyses of each spine simple, not branched, with thin condyles. Large meshes of the shell ten to twenty times as broad as the bars. This and the following species greatly resemble the simplest forms of Phractaspis (Pl. , figs. 1, 2); they differ from these, however, by the equal size and distance of the four branches of each spine, which thus form a rectangular cross.

Dimensions.—Diameter of the shell 0.1; breadth of the spines and bars 0.002.

Habitat.—Central Pacific, Station 268, surface.

2. Stauraspis xiphacantha, n. sp.

Radial spines stout, cylindrical in the inner half, conical in the shorter outer half. Four apophyses of each spine simple, not branched, broad, with thick condyles. Meshes of the shell six to eight times as broad as the bars.

Dimensions.—Diameter of the shell 0.12; breadth of the spines and bars 0.008 to 0.01.

Habitat.—South Pacific, Station 290, surface.

Subgenus 2. Stauraspidium, Haeckel.

Definition.—Apophyses of the spines branched; therefore each spine with eight to twenty or more sutural condyles.

3. Stauraspis furcata, n. sp.

Radial spines thin, quadrangular, prismatic; outer and inner halves nearly of equal length. The four apophyses of each spine simply forked (or partly with bifid fork-branches); each spine with eight to twelve sutural condyles. Meshes of the shell ten to twenty times as broad as the bars.

Dimensions.—Diameter of the shell 0.15; breadth of the spines and bars 0.003.

Habitat.—Central Pacific, Station 266, surface.

4. Stauraspis stauracantha, n. sp. (Pl. , figs. 5, 6).

Radial spines thin, in the inner longer half cylindrical, in the outer half conical with thickened base. Four apophyses of each spine doubly forked or dichotomously (more or less irregularly) branched; each spine with sixteen to twenty-four sutural condyles. Meshes of the shell of very different sizes and forms; the largest ten to fifteen, the smallest two to three times as broad as the bars.

Dimensions.—Diameter of the shell 0.14; breadth of of the spines 0.002 to 0.01, of the bars 0.002.

Habitat.—Tropical Atlantic, Station 343, surface.

Genus 359. Echinaspis, 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 bearing by-spines.

The genus Echinaspis exhibits the same structure of the shell as its ancestral form Stauraspis, and differs from it only in the development of by-spines on the sutural condyli.

1. Echinaspis dichotoma, n. sp.

Radial spines cylindrical, thin, outer half longer than the inner. Four apophyses of each spine simply forked (or partly with bifid fork-branches); therefore each spine usually possesses eight (sometimes ten to twelve) sutural condyles. Meshes of the shell ten to twelve times as broad as the bars. Each condyle bears a zigzag by-spine, half as long as the radius.

Dimensions.—Diameter of the shell 0.12, of the spines 0.004 to 0.006.

Habitat.—North Pacific, Station 253, surface.

2. Echinaspis diadema, n. sp.

Radial spines thin and long, quadrangular, prismatic; outer half two to three times as long as the inner. Four apophyses of each spine simply forked (or partly with bifid fork-branches); each spine with eight to twelve sutural condyles. Meshes of the shell fifteen to twenty-five times as broad as the bars. Each condyle bears a simple bristle-shaped by-spine, nearly as long as the radius.

Dimensions.—Diameter of the shell 0.11; breadth of the spines and bars 0.002.

Habitat.—South Atlantic, Station 333, surface.

3. Echinaspis echinoides, n. sp. (Pl. , figs. 7,8).

Radial spines roundish, in the outer half conical, and two to three times as broad as in the inner half. Four apophyses of each spine doubly forked or dichotomously (more or less irregularly) branched; each spine with sixteen to twenty-four sutural condyles. Meshes of the shell four to eight times as broad as the bars. Each condyle bears a zigzag by-spine, one-third as long as the radius.

Dimensions.—Diameter of the shell 0.15; breadth of the spines 0.004 to 0.01, of the bars 0.002.

Habitat.—Central Pacific, Station 266, surface.

Genus 360. Zonaspis, n. gen.

Definition.—Dorataspida with four plates, each of which is perforated by four crossed aspinal pores; these four plates are formed by the united branches of the other spines (eight polar and eight tropical) form no lattice-plates by union. Each condyle bears a by-spine.

The genus Zonaspis differs from all other Dorataspida in the peculiar formation of the four equatorial spines, which form by union of the recurved branches of their apophyses four perforated plates (each with four crossed pores), whilst the branches of the sixteen other plates do not unite to form plates, but simply meet the branches of the neighboring spines.

1. Zonaspis fragilis, n. sp.

Radial spines very thin and long, cylindrical. Four meshes of each equatorial plate pentagonal, ten to twelve times as broad as the bars. By-spines zig-zag, nearly as long as the radius.

Dimensions.—Diameter of the shell 0.16, of the parmal pores 0.018.

Habitat.—South Atlantic, Station 332, surface.

2. Zonaspis cingulata, n. sp. (Pl. , figs. 3, 4).

Radial spines cylindrical in the inner half, with thickened pyramidal bases (fig. 3), conical in the outer half; both halves of equal length. The four meshes of each equatorial plate egg-shaped, four to six times as broad as the bars. By-spines zigzag, half as long as the radius.

Dimensions.—Diameter of the shell 0.15, of the parmal meshes 0.015.

Habitat.—Tropical Pacific (east coast off Philippines), Station 275, surface.

3. Zonaspis æquatorialis, n. sp. (Pl. , fig. 5).

Radial spines stout, cylindrical in the shorter inner half, conical in the longer outer half. The four meshes of each equatorial plate circular, only twice as broad as the bars. By-spines zigzag, nearly as long as the radius.

Dimensions.—Diameter of the shell 0.11, of the parmal meshes 0.008.

Habitat.—Equatorial Atlantic, Station 347, surface.

Genus 361. Dodecaspis, n. gen.

Definition.—Dorataspida with twelve plates, each of which is perforated by four crossed aspinal pores; these twelve plates are formed by the united branches of the apophyses of four equatorial and eight polar spines. The branches of the apophyses of the eight tropical spines form no lattice-plates by union. Each condyle bears a by-spine.

The genus Dodecaspis differs from all other Dorataspida in the peculiar composition of its shell; twelve spines (four equatorial and eight polar spines) form by union of the branches of their apophyses twelve plates, each of which exhibits four crossed pores, whilst the eight other (tropical) spines form no perforated plates, but simply unite with the neighbouring spines by meeting branches. Some irregularity is often to be found in this genus; instead of four pores in each plate there may be two closed, the other two which are opposite being open. Several times I observed a peculiar "hemihedral" variety: only six spines of one meridian plane (the two equatorial and the four polar spines of the "hydrotomical" plane) exhibited complete shields, whilst the branches of the other fourteen plates remained open. This "hemihedral" form may perhaps represent a peculiar genus, Hemiaspis.

1. Dodecaspis tricinata, n. sp. (Pl. , fig. 1).

Radial spines thin and long, cylindrical. The four meshes of each equatorial and each polar plate of equal size, pentagonal, about eight times as broad as the bars. By-spines zigzag, nearly as long as the radius. In this species the hemihedral variety, Hemiaspis, often occurs.

Dimensions.—Diameter of the shell 0.15, of the parmal pores 0.016.

Habitat.—South-east Pacific (west coast of Patagonia), Station 302, surface.

2. Dodecaspis trizonia, n. sp.

Radial spines thin, cylindrical in the longer inner half, conical in the shorter outer half. The four meshes of each equatorial and each polar plate of equal size, roundish or nearly circular, five to six times as broad as the bars. By-spines straight, denticulated, scarcely half as long as the radius.

Dimensions.—Diameter of the shell 0.12, of the parmal pores 0.012.

Habitat.—South-west Pacific (east coast of New Zealand), Station 169, surface.