l!i;P()in' ON 'I'HK IJADHtl.AIM A. \U'> 



five to six on the radius. Between every three meshes arises n short radial ihorn, as long as the 

 tliickness of the shell-wall. Six radial spines sceptre-sliaped, six-sided, somewhat constricted 

 towards their middle part, strong, as long as the radius of the outer shell, as broad as one of its 

 meshes. Eadial proportion of the three spheres =1 : 2 : 6. Pores of tlie two inner shells regular 

 hexagonal, with thin bars, six to eight on the half meridian (fig. la). 



Dimensions. — Diameter of the outer shell O'lo, of the middle 0'04, of the inner 0'02 ; pores of 

 the outer shell n-Ol, of tlu^ nnddle fl-flOS, of the inner n-0n4 ; length of the six spines 0-06, liasal 

 breadth O-Ola. 



Hahifaf. — Equatorial Atlantic, Station .'UT, surface. 



11. He.raconthim prionacanthmn, u. sp. (PI. 24, figs. 7, 7o). 



Cortical shell thick walled, thorny ; its pores regular circular, with elevated hexagonal frames 

 six to nine on the radius, twice as broad as the crest-shaped bars. At each nodal-point of the 

 hexagon arises one short conical papilla or thorn. Eadial proportion of the three spheres = 

 1 : o : 10. Pores of both medullary shells much smaller, regular circular. Six main spines three- 

 sided prismatic, longer than the radius of the outer shell, as broad as one of its meshes ; their three 

 edges serrated, with ten to twelve teeth. 



Dimensions. — Diameter of the outer shell 015, middle 0-045, inner 0'015 ; cortical pores O'Ol, 

 bars 0'005 ; length of the spines Ol, breadth 0-012. 



Hahitat. — West Tropical Pacific, Station 225, depth 4475 fathoms. 



12. Hexacontium clavigerum, u. sp. (PI. 23, fig. 5). 



Cortical shell very thick walled, thorny; its pores regular circular, hexagonally framed, three 

 times as broad as the bars, nine to twelve on the radius ; between them short conical papilhe or thorns 

 arising at the nodal-points. Eadial proportion of the three spheres = 1 : 2 : 5. Outer medullary shell 

 with regular circular, much smaller pores ; connected with the cortical shell by numerous (twenty to 

 thirty) thin radial beams. Six main spines very stout, club-shaped, scarcely as long as the radius 

 of the outer shell, three times as In-oad as one of its pores, three-sided, with three to four teeth on 

 each edge. 



Dimensions. — Diameter of the outer shell 0-2, of the middle U'08, of the inner 0-04 ; cortical 

 pores 0-012, bars 0-004 ; length of the six spines O'OS, breadth 0-0:3. 



Ealitat. — Soiith Atlantic, Station :>;12, depth 2200 fathoms. 



13. Hexaconfium Jfni'idiiitu n. sp. (PL 24, fig. 4). 



Cortical shell papillose, thick walled. Pores regular, six-lobed, four limes as broad as the bars, 

 tl\-e to seven on the radius ; each pore with six (sometimes also fi^e or seven) concave indentations oi- 

 liibules; between the pores at the nodal-points arise short conical papilla- or thorns. Eadial pro- 

 ])ortion of the three spheres = 1 : 2 : 3. Eadial main spines pommel-shaped, three-sided prisniatii\ 

 longer than the radius of the outer shell, two to three times as broad as one pore. 



