194 THE VOYAGE OF Il.^r.S. CHALLENGEE. 



every six pores arises a small, Lrislle-shaped, raiHal 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 liexagonal meshes and smooth surface. 

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



Dimensions. — Diameter of the outer shell 0"12, middle O'l, inner 0'03 ; pores of the middle 

 shell 0-004, bars 0-001 ; length of the spines 0-025, basal breadth O-Ol. 



Habitat. — Central Pacific, Station 27-4, deptli 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 Ijristle-shaped, radial spines 

 (other than the six main spines). 



8. Hcntcuiititim liexayoiioU', u. sp. 



Cortical sliell thin walled, bristly, with \ery delicate network ; its pores regular hexagonal, 

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

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

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

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

 medullary sliells also regular hexagonal, but nmch smaller, in the middle shell eleven to twehe, in 

 the iimer, six to seven on the half meridian. 



Dimcnsimis. — Diameter of the outer shell 0'12, of the middle 0*06, of tlie inner iyO''<: meshes 

 of the outer shell O'OOS ; length of the six spines 0-05, l>asal thickness O'OOS. 



ffabituf. — Indian Ccean, Ceylon, surface, Haeckel. 



9. Hexacontiuui fivcosuiu, 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 sheU-waU. Six racUal spmes \-ery sliort and stout, three- 

 sided pyramidal, scarcely half so long as the radius of the outer sliell. Padial i)roporlii;in of th 

 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 0-1 to 0-12, of the middle 0-04 to 0-05, of the inner 

 0-02 ; meshes of the outer shell 0-008; length of the six spines 0-2 to Q'o, basal breadth 0-015. 



Eahitat. — Central Pacific, Station 265, depth 2900 fathoms. 



10. Hexacontium sceptrutn, n. sp. (PL 24, tigs. I, la). 



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

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



(.' 



