Shell nut-shaped, compressed, smooth, with prominent sagittal ring. On each side of the ring three to four pairs of very large annular polygonal pores. Lateral pores small and numerous, roundish. Basal plate with two large pores only. Horn slender, conical, shorter than half the shell. _Dimensions._--Shell 0.11 long, 0.13 broad. _Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. 2. _Circospyris gigas_, Haeckel. _Dictyospyris gigas_, Ehrenberg, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 68, Taf. xix. fig. 6. Shell nut-shaped, tuberculate, with distinct sagittal stricture. On each side of the ring four pairs of larger annular pores. Lateral pores roundish, smaller. Basal plate with four large central and a circle of eight to twelve smaller peripheral pores. Horn cylindrical, about half as long as the shell (in the inverted figure of Ehrenberg directed downwards). _Dimensions._--Shell 0.1 to 0.15 long, 0.15 to 0.2 broad; horn 0.05 to 0.08 long. _Habitat._--Fossil in Barbados. 3. _Circospyris tridentata_, Haeckel. _Dictyospyris tridentata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 70, Taf. xix. fig. 10, _a_, _b_. Shell nut-shaped, smooth, with sharp sagittal stricture. On each side of the ring two pairs of large annular pores. Lateral pores roundish, smaller. Basal plate with six large pores. Horn slender, cylindrical, about as long as the shell, with three sharp teeth at the distal end. _Dimensions._--Shell 0.03 long, 0.05 broad; horn 0.03 long. _Habitat._--Fossil in Barbados. {1073}Genus 468. _Dictyospyris_,[86] Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 54. _Definition._--#Zygospyrida# without basal feet, and without coryphal horns. The genus _Dictyospyris_, the last and simplest of the twenty-eight genera of Zygocyrtida, may be regarded either as a primordial ancestral form of this large family, or more probably as the last and most reduced form of it. In the former case the total absence of coryphal horns and basal feet is primary, in the latter case secondary, effected by phylogenetic reduction and loss. But it is also possible that in one part of the numerous species of this genus the former case, and in another the latter takes place, and that one part of _Dictyospyris_ may be directly developed from the Semantida or Coronida (the lattice shell becoming complete), another part arising from the Tripospyrida or Dipospyrida (the horns and feet becoming lost). Subgenus 1. _Dictyospyrantha_, Haeckel. _Definition._--Basal plate with two large pores only (the primary jugular pores of _Semantis_). 1. _Dictyospyris distoma_, n. sp. (Pl. 89, figs. 11, 12). Shell nut-shaped, smooth, or somewhat tuberculate, with deep sagittal stricture. Pores not numerous, large, roundish-polygonal; three pairs of large annular pores on each side of the ring. Basal plate with two very large pentagonal roundish collar pores. _Dimensions._--Shell 0.06 long, 0.08 broad.