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



every six pores arises a small, bristle-shaped, radial spine, as long as the diameter of one pore. The 

 distal ends of all these spines are connected by very delicate tangential threads, and consequently 

 form by their attachment an outer cortical shell, with regular hexagonal meshes and smooth surface. 

 Six main spines short, three-sided prismatic, scarcely as long as half the radius of the outer shell. 



Dimensions. Diameter of the outer shell 012, middle 01, inner 0'03 ; pores of the middle 

 shell 0-004, bars O'OOl ; length of the spines 0'025, basal breadth O'Ol. 



Habitat. Central Pacific, Station 274, depth 2750 fathoms. 



Subgenus 2. Hexacontella, Haeckel. 



Definition. Pores of the cortical shell regular or subregular, of nearly equal size and 

 similar form; surface covered with numerous conical or bristle-shaped, radial spines 

 (other than the six main spines). 



8. Hexacontium hexagonale, 11. sp. 



Cortical shell thin walled, bristly, with very delicate network ; its pores regular hexagonal, 

 twelve to sixteen on the radius, ten to twelve times as broad as the thin thread-like bars. At each 

 nodal-point of the network (between every three meshes) arises a bristle-shaped, radial spine, as long 

 as the diameter of one mesh. Six main spines hexagonal, as long as the radius of the outer shell, us 

 broad at its base as one mesh. Eadial proportion of the three spheres = 1 : 2 : 4. Pores of botli 

 medullary shells also regular hexagonal, but much smaller, in the middle shell eleven to twelve, in 

 the inner, six to seven, on the half meridian. 



Dimensions. Diameter of the outer shell 012, of the middle 0'06, of the inner O'Oo ; meshes 

 of the outer shell O'OOS ; length of the six spines 0'05, basal thickness O'OOS. 



Habitat. Indian Ocean, Ceylon, surface, Haeckel. 



9. Hexacontium favosum, n. sp. (PI. 24, figs. '2, 2a). 



Cortical shell very thick walled, spiny, with regular, honeycomb-like network ; its meshes funnel- 

 shaped, with circular inner, hexagonal outer aperture, twice as broad as the bars ; five to seven on 

 the radius. Between every three meshes (at each corner of the hexagon) arises a short radial 

 thorn, not so long as the thickness of the shell-wall. Six radial spines very short and stout, three- 

 sided pyramidal, scarcely half so lung as the radius of the outer shell. Uadial proportion of the 

 three spheres =1:2:5. Pores of both medullary shells regular, circular, about as broad as the 

 bars, six to eight on the half meridian. 



Dimensions. Diameter of the outer shell 01 to 012, of the middle (K)4 to O'Uo, of the inner 

 0'02 ; meshes of the outer shell O'OOS ; length of the six spines 0'2 to 0'3, basal breadth O'Olo. 



Habitat. Central Pacific, Station 265, depth 2900 fathoms. 



10. Hexacontium sceptrum, n. sp. (PL 24, figs. 1, la). 



Cortical shell thick walled, spiny, with regular, honeycomb-like network ; its meshes tunnel- 

 shaped, with circular inner, hexagonal outer aperture, three to four times as broad us the bars ; 



