1246 THE VOYAGE OF H.M.S. CHALLENGER. 



Subgenus 5. Enneaphormis, Haeckel, 1881, Prodromus, p. 432. 



Definition. Thorax with nine radial ribs, three of which are the primary beams, 

 the other six being secondary and interpolated. 



9. Sethophormis rotuta,, n. sp. (PI. 57, fig. 9). 



Enneatphormis rotula, Haeckel, 1881, Prodromus et Atlae, pi. Ivii. fig. 9. 



Cephalis very large, flat, cap-shaped,, trilobed, with irregular, polygonal network. Horizontal 

 collar-ring stout, hexagonal, with three larger and three alternate smaller sides of half the length. 

 From the middle of the three larger sides arise three horizontal, centripetal, radial beams, which are 

 united in the centre of the collar-septum the three primary cortinar beams. These are prolonged 

 outside into three centrifugal primary ribs of the thorax. Prom the six corners of the collar-ring 

 arise six other secondary, thoracic ribs, equal in size and similar in form to the three primary. 

 Each of these nine equal, straight ribs of the thorax is thickened towards the distal end, and bears 

 at equal distances five pairs of opposite (tangential) lateral branches. The opposite branches of the 

 neighbouring spines become united, and lie nearly horizontally in one plane, so that the Hat, dis- 

 coidal thorax is like a nine-angled wheel with nine equally distant spokes and five concentric, nine- 

 angled rings. 



Dimensions. Cephalis 012 diameter, thorax 0'36 diameter. 



Habitat. Central Pacific, Stations 270 to 274, depth 235.0 to 2925 fathoms. 



10., Sethophormis triloba, n. sp. 



Cephalis large, hemispherical, distinctly trilobed, with dense, irregular, polygonal network. From 

 the centre of its top diverge three stout arches or semilunar rods, which are curved downwards, and 

 unite with the three horizontal, radial beams of the collar-septum inside the collar-ring. These three 

 parietal arches of the cephalis are much stronger than in the similar preceding species (PL 57, fig. 9), 

 and between them are placed three vaulted bosoms of the cephalis. The collar-ring and the thorax 

 are of the same form as in the preceding, but possess only four concentric, nine-angled rings. 



Dimensions. Cephalis 0'05 long, 0'08 broad ; thorax 0'24 diameter. 



Habitat. North Pacific, Station 244, depth 2900 fathoms. 



11. Sethophormis enncastrum, n. sp. 



Cephalis very large, flat, cap-shaped, with hexagonal base, trilobed, of similar form and struc- 

 ture to the two preceding species. The flat, discoidal thorax has also the same form, with nine stout 

 ribs and five concentric, ,nine-angled rings ; its forty-five large meshes, however, are not so simple 



