12. Stylodictya hertwigii, Haeckel.
All rings of the disk convoluted in a simple regular spiral, with increasing breadth from the centre; the fifth ring twice as broad as the second. Pores regular, circular, two on the breadth of each ring. Twelve piercing radial beams and some others interrupted, prolonged into twelve to twenty radial marginal spines, bristle-shaped, about as long as the diameter of the disk.
Dimensions.—Diameter of the disk (with five rings) 0.15; breadth of the second ring 0.01, of the fifth 0.02; pores 0.006.
Habitat.—Mediterranean (Messina), R. Hertwig.
13. Stylodictya dujardinii, Haeckel.
All rings of the disk convoluted in a simple regular spiral, of nearly equal breadth. Pores regular, circular, two on the breadth of each ring. Very numerous (twenty to thirty or more) piercing radial beams, prolonged into bristle-shaped marginal spines, about as long as the diameter of the disk.
Dimensions.—Diameter of the disk (with six rings) 0.12; breadth of each ring 0.01; pores 0.004.
Habitat.—Mediterranean (Messina), Haeckel.
14. Stylodictya echinastrum, Ehrenberg.
All rings of the disk convoluted in a double spiral, of nearly equal breadth. Pores irregular, roundish, two to three on the breadth of each ring. Marginal spines numerous, twenty to thirty, of very different size, the largest conical, strong, about as long as the diameter of the disk, and on the base as broad as one ring.
Dimensions.—Diameter of the disk (with five rings) 0.12; breadth of each ring 0.01; pores 0.002 to 0.006.
Habitat.—Fossil in the rocks of Barbados.
15. Stylodictya clavata, Ehrenberg.
All rings of the disk convoluted in a half spiral, of nearly equal breadth; each ring by four zigzag beams (crossed in two perpendicular diameters) divided into four equal quarters; the spiral line of each quarter ring halving both neighbouring quarters. Pores regular, circular, two on the breadth of each ring. Eight marginal spines short, conical, with thin pedicle; four perradial (as
