Shell polyhedral, with deep sagittal stricture, studded with fifty to seventy prismatic spines; two inferior (pectoral) spines about as long as the shell, the others much shorter. Pores polygonal. On the frontal and the occipital face one pair of very large pores. Basal plate with two distinctly hexagonal pores. Bars of the loose network prismatic. Dedicated to my dear friend, the excellent author and painter, Ludwig Mulder, of the Hague. _Dimensions._--Shell 0.07 long, 0.12 broad; spines 0.01 to 0.08. _Habitat._--Indian Ocean, Sunda Straits (Rabbe), surface. 5. _Ceratospyris strasburgeri_, n. sp. (Pl. 86, fig. 2). Shell polyhedral, with slight sagittal stricture, studded with thirty to forty prismatic spines, which are about half as long as the shell (two or four inferior are longer). Pores roundish, with polygonal frames. On the frontal and occipital face two pairs of larger pores (the superior {1068}smaller). Basal plate with two large pentagonal pores. Bars of the network prismatic. Dedicated to my dear friend, the celebrated botanist, Professor Eduard Strasburger, of Bonn. _Dimensions._--Shell 0.07 long, 0.1 broad; spines 0.02 to 0.04. _Habitat._--Western Tropical Pacific, Station 225, depth 4475. 6. _Ceratospyris mülleri_, Stöhr. _Ceratospyris mülleri_, Stöhr, 1880, Palæontogr., vol. xxvi. Taf. iii. fig. 15. Shell polyhedral, with slight collar stricture, studded with forty to fifty pyramidal spines, shorter than half the shell. Pores circular, with pentagonal frames of the same breadth, all nearly of equal size. (Basal plate with four pores?) Bars of the network prismatic. Dedicated to Johannes Müller. _Dimensions._--Shell 0.08 long, 0.1 broad; spines 0.01 to 0.03. _Habitat._--Fossil in Tertiary rocks of Sicily, Grotte (Stöhr). 7. _Ceratospyris krausei_, n. sp. (Pl. 86, fig. 10). Shell nut-shaped, with deep sagittal stricture, studded with forty to fifty strong conical spines; six basal spines as long as the shell and two to three times as long as the others. Pores roundish polygonal, twice to three times as broad as the bars; two pairs of larger pores on each side of the ring. (Basal plate with four large pores?) Bars of the network rounded, thick. Dedicated to my dear friend, the excellent author, Ernst Krause (Carus Sterne), of Berlin. _Dimensions._--Shell 0.06 long, 0.09 broad; spines 0.03 to 0.08. _Habitat._--Western Tropical Pacific (Philippine Sea), Station 206, depth 2100 fathoms. 8. _Ceratospyris preyeri_, n. sp. (Pl. 86, fig. 9). Shell nut-shaped, with slight sagittal stricture, studded with ten to twelve longer club-shaped spines (about as long as the shell) and numerous smaller conical spines. Pores irregular, roundish, numerous; two pairs of larger pores on each side of the ring. Basal plate with four large pores. Bars of the network rounded. Dedicated to my honoured friend and colleague, the celebrated investigator of psychical ontogeny, Professor William Preyer, of Jena.