4. _Semantidium signatorium_, n. sp. (Pl. 92, fig. 7). Sagittal ring semicircular, thorny; basal ring pentagonal, with short spines on the margin and five stronger thorny spines on the five corners. Jugular pores ovate, smaller than the triangular cervical pores. Cardinal pores two to three times as large as each of the former, pentagonal. _Dimensions._--Height of the sagittal ring 0.08, breadth 0.12. _Habitat._--North Pacific, Station 341, depth 2300 fathoms. Genus 410. _Clathrocircus_,[29] Haeckel, 1881, Prodromus, p. 447. _Definition._--#Semantida# with a variable number of pores on the apical and the basal part of the ring, symmetrically arranged, without typical basal feet. The genus _Clathrocircus_ comprises those Semantida in which the sagittal ring bears not only basal pores (as in the three preceding genera) but also apical pores (on the opposite pole of the main axis), or a variable number of pores along the whole ring. All these pores are symmetrically arranged in pairs. In the simplest form there are only two apical pores opposite to four basal pores, whilst in the highest state of development the whole ring bears two complete circles of pores. At both poles of the transverse axis two large lateral gates remain open. If these become closed by lattice-work, _Clathrocircus_ passes over into _Dictyospyris_. {962}1. _Clathrocircus hexaporus_, n. sp. Sagittal ring circular, smooth, with three pairs of pores (one apical and two basal). The two apical pores are triangular with two lateral spines, and correspond to the two mitral gates of the Tympanida. The four basal pores form a hexagonal basal plate, with six lateral spines, and correspond to the four basal pores of _Semantrum_; the two jugular are pear-shaped, and half as broad as the two triangular cardinal pores. _Dimensions._--Height of the sagittal ring 0.08, breadth 0.06. _Habitat._--Cosmopolitan; Atlantic, Pacific, many Stations, surface. 2. _Clathrocircus octoporus_, n. sp. Sagittal ring elliptical, smooth, with four pairs of pores (two apical and two basal). The four apical pores are of nearly equal size, subcircular, and form a regular cross around the apical pole. The four basal pores are ovate, and form a quadrangular plate, armed with marginal thorns; the two jugular pores are somewhat smaller than the two cardinal pores. _Dimensions._--Height of the sagittal ring 0.11, breadth 0.08. _Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms. 3. _Clathrocircus decaporus_, n. sp. Sagittal ring ovate, thorny, with five pairs of pores (two apical and three basal). The four apical pores are roundish and form a cross. The six basal pores are triangular and form a hexagonal plate with thorny margin; the two jugular pores are somewhat larger than the two cervical, and half as broad as the two cardinal pores. _Dimensions._--Height of the sagittal ring 0.09, breadth 0.07. _Habitat._--North Pacific, Station 256, depth 2950 fathoms.