Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal constriction, armed with numerous irregular spines, which are partly simple, partly branched. Sagittal ring thicker and lower, only half as high, with a few short conical spines at the apical and basal poles. _Dimensions._--Height of the frontal ring 0.12, breadth 0.18. _Habitat._--South Atlantic, Station 332, depth 2200 fathoms. 7. _Zygostephanus bicornis_, n. sp. (Pl. 93, fig. 2). Frontal ring violin-shaped, on the upper and the lower margin concave, with a deep sagittal constriction; its two halves pentagonal. Between numerous smaller spines there arise from the frontal ring six groups of larger branched spines, two odd in the corners of the highest points (curved like two horns), two branched pairs on the prominent lateral corners (at right and left), and two pairs in the corners of the lowest points (like four branched basal feet). Sagittal ring only two-thirds as high, with four pairs of irregular spines. _Dimensions._--Height of the frontal ring 0.11, breadth 0.16. _Habitat._--South Pacific Station 300, depth 1375 fathoms. Genus 415. _Zygostephanium_,[34] Haeckel, 1881, Prodromus, p. 446. _Definition._--#Coronida# with four large, partly latticed, lateral gates, without basal gate. Skeleton composed of two meridional rings perpendicular to each other. The genus _Zygostephanium_ differs from the preceding ancestral genus _Zygostephanus_ in the development of lattice-work along the two crossed rings, produced by their anastomosing branches. Therefore the four large lateral gates between them, which are quite simple, in the preceding genus here become more or less fenestrated. {973}1. _Zygostephanium dizonium_, n. sp. (Pl. 93, fig. 3). _Tympaniscus dizonius_, Haeckel, 1882, Manuscript. Both rings elliptical, of nearly equal height, smooth, without spines. Sagittal ring with four pairs of small pores (two apical pairs and two basal pairs). Frontal ring with three pairs of small pores (one pair lateral, one pair above and one pair below). _Dimensions._--Height of the frontal ring 0.08, breadth 0.12. _Habitat._--Central Pacific, Station 268, depth 2900 fathoms. 2. _Zygostephanium paradictyum_, n. sp. (Pl. 93, fig. 4). Frontal ring kidney-shaped, in the upper half convex, in the lower concave, in the latter with a deep sagittal constriction. Sagittal ring ovate, about two-thirds as high as the frontal ring. Both rings three-edged, armed with numerous short and branched bristle-shaped spines, which anastomose along their three edges and produce two series of irregular polygonal pores. _Dimensions._--Height of the frontal ring 0.08, breadth 0.13. _Habitat._--North Pacific, Station 236, surface. 3. _Zygostephanium constrictum_, n. sp.