Discospira duplex, Stöhr, 1880, Palæontogr., vol. xxvi. p. 114, Taf. vi. fig. 4.
All rings of the disk spirally convoluted, in a perfect double spiral, with increasing breadth of the broad rings. Pores regular, circular; in the inner rings two to three, in the outer four to five on the breadth. Radial beams interrupted. Margin of the rings thorny.
Dimensions.—Diameter of the disk (with three rings) 0.15; breadth of the rings 0.02 to 0.04; pores 0.007.
Habitat.—Fossil in Tertiary rocks of Sicily, Grotte, Stöhr.
19. Porodiscus semispiralis, n. sp. (Pl. [41], fig. 4).
All rings of the disk spirally convoluted, divided by four radial, perpendicularly crossed and zigzag shaped beams into four quadrants; the quarter rings of each quadrant halving the rings of each adjacent quarter. Half spiral line often irregular or partly interrupted. Breadth of all rings nearly equal. Pores irregular, roundish, two on the breadth of each ring. Margin of the disk dentated.
Dimensions.—Diameter of the disk (with nine rings) 0.22; breadth of each ring 0.012; pores 0.002 to 0.006.
Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.
Subgenus 5. Atactodiscus, Haeckel, 1881, Prodromus, p. 459.
Definition.—Rings of the disk more or less irregular, partly concentric, partly spirally convoluted, often interrupted.