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



20. Hexacontium yladiatum, n. sp. (PI. 25, fig. 8). 



Cortical shell very thick walled, spiny, with irregular network ; its meshes roundish, two 

 to five times as hroad as the bars, of very different size, ten to fifteen on the half 

 meridian. Bars between them very strong, three-sided prismatic, armed with a great number 

 of small thorns, and with larger spines at the nodal-points between every three meshes. 

 Radial proportion of the three spheres = 1:3:12. Six strong radial main spines three- 

 sided prismatic, with three prominent, somewhat contorted wings, acute, broader than the 

 diameter of the inner shell and as long as the diameter of the outer shell. These six 

 main spines are situated in the same three dimensive axes as the six thin radial beams 

 connecting the two medullary shells. But the six radial beams which connect the middle with 

 the outer shell alternate with the former and lie in three other dimensive axes, a very 

 rare and remarkable disposition. 



Dimensions. Diameter of the outer shell 0'2, middle O05, inner 0'016 ; cortical pores O'Ol to 

 0-03, bars 0'006 ; length of the six spines 0'2, breadth 0'02 to 0-03. 



Habitat. Tropical Atlantic, Station 342, depth 1445 fathoms, 



21. Hexacontium setosum, n. sp. 



Cortical shell thin walled, covered with numerous bristle-shaped, simple, radial by-spines of 

 variable length. Pores irregular roundish, five to seven on the radius, two to eight times 

 as broad as the bars. Radial proportion of the three spheres = 1 : 3 : 9. Main spines three- 

 sided pyramidal, as long as the radius. 



Dimensions. Diameter of the outer shell 01 to 015, middle 0'035 to 0'05, inner 0-013 to 

 0-016 ; cortical pores O'Ol to 0'03, bars 0'003 to 0-004 ; length of the six spines O'Oo to 0'08, 

 basal breadth 0'012 to O'Olo. 



Habitat. Cosmopolitan ; Mediterranean, Atlantic, Pacific, surface ; also fossil in Barbados. 



22. Hexacontium furcatum, n. sp. 



Cortical shell thin walled, covered with numerous thin, bristle-si laped by-spines, which are 

 forked and nearly as long as the main spines. Pores irregular roundish, eight to ten on 

 the radius, two to eight times as broad as the bars. Radial proportion of the three 

 spheres = 1 : 2'5 : 10. Main spines triangular pyramidal, shorter than the radius. 



Dimensions. Diameter of the outer shell 018, middle - 045, inner Oi)18 ; cortical pores 0-005 

 to O'Olo, bars 0'002 ; length of the six spines 0'07, basal breadth 0'015. 



Habitat. North Atlantic, Station 3.">4. surface. 



23. Hexacontium drymodes, Haeckel. 



Acthwmma dnjmodeg, Haeckel, 18C2, Monogr. d. Radio!., p. 442, Taf. xxiv. fig. 9. 



Cortical shell thin walled, covei-ed with numerous thin, bristle-shaped spines, which are double 

 forked and half as long as the main spines. Pores irregular roundish, eight to ten on the radius, 



