Stylodictya ocellata, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxiii. fig. 7.

All rings of the disk irregular, not concentric, half-spiral, interrupted by four zigzag-shaped, crossed, radial beams; the quarter ring of each quadrant halving both neighbouring quarters. Breadth of the rings increasing towards the periphery; the fourth ring twice as broad as the second. Pores irregular, with increasing size from the centre, three on the breadth of each ring. Four marginal spines thick and long, cylindrical; margin between them smooth.

Dimensions.—Diameter of the disk (with four rings) 0.1; breadth of the inner rings 0.01, of the outer 0.02; pores 0.002 to 0.006.

Habitat.—Fossil in the rocks of Barbados.

Stylodictya haeckelii, Zittel, 1876, L. N. [29], p. 85, Taf. ii. fig. 9, is a fossil Cretaceous species, related to Stylodictya multispina.

Genus 221. Stylodictya,[[260]] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54.

Definition.—Porodiscida with numerous (five or more, commonly eight to twelve) solid radial spines, regularly or irregularly disposed on the margin of the circular or polygonal disk; margin simple, without a porous equatorial girdle.

The genus Stylodictya comprises the majority of this subfamily, in which the number of the marginal spines exceeds four. Commonly we find eight to twelve spines, more or less regularly disposed (four perradial and four interradial, or four perradial and eight adradial); but often also the number and disposition become irregular (sometimes very large). In my Monograph (1862 pp. 495, 515) I had separated the concentric disks with closed circular rings (as true Stylodictya, s. str.) from the spiral disks with convoluted rings (Stylospira). But I retain these two groups here only as two subgenera, as intermediate forms between them are very common, and often a part of the disk concentric, a part spiral (compare above, p. [492]).

Subgenus 1. Stylodictyon, Haeckel, 1862, Monogr. d. Radiol., p. 495.

Definition.—All rings of the disk concentric, commonly circular (rarely a little elliptical or polygonal).