Page:Scientific results HMS Challenger vol 18 part 2.djvu/818

Synopsis of the Genera of Circoporida.

I. Subfamily Circogonida. Shell spherical or polyhedral with panelled structure and polygonal plates. A certain number of radial spines are geometrically disposed.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \\\ \\\ \ \end{matrix}}\right.}$	Shell octahedral (or spherical),		Six radial spines,	711. Circoporus.
		Shell tetradecahedral,		Nine radial spines,	712. Circospathis.
		Shell icosahedral,		Twelve radial spines,	713. Circogonia.
		Shell dodecahedral,		Twenty radial spines,	714. Circorrhegma.
		Shell polyhedral,		Twenty-four to forty or more radial spines,	715. Circostephanus.
II. Subfamily Haeckelinida.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Shell spherical, with dimpled structure, and a variable number of radial spines (without polygonal plates),			716. Haeckeliana.

Subfamily 1. Circogonida, Haeckel.

Definition.—Circoporida with panelled shell, composed of polygonal plates. The shell is usually polyhedral, more rarely spherical, and the radial spines are usually (or perhaps constantly) branched and regularly arranged.

Genus 711. Circoporus,^[1] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 5.

Definition.—Circoporida with a spherical or regularly octahedral shell, composed of eight congruent, triangular plates, with six corners from which arise six radial spines, opposite in pairs in three diameters, perpendicular one to another.

The genus Circoporus, the simplest among the Circoporida, is distinguished by the regular octahedral form of the shell, with the three equal axes of the regular crystalline system perpendicular one to another. Six equal radial spines, arising from the six corners, lie opposite in pairs in those three dimensive axes. The eight equal triangular faces of the octahedron are sometimes plane, sometimes concave or convex, and sometimes the shell becomes spherical. In this case it becomes very similar to the Hexastylida among the Sphæroidea.

1. Circoporus sexfurcus, Haeckel (Pl. 117, fig. 5).

Challengeria sp., John Murray, 1876, Proc. Roy. Soc. Lond., vol. xxiv. pl. xxiv. fig. 5.

Shell spherical, covered with irregular, polygonal plates. Six radial spines shorter than the diameter of the shell, covered with thin curved bristles, in the proximal half cylindrical, in the distal half forked, each with two equal curved fork-branches. Around the ciliated base of each spine a

1. Circoporus = Shell with circles of pores; κίρκος, πόρος.