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



2. Spongostijlus gladiatus, Haeckel. 



SttjJvsphm-a hoJoqjhwm, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, 

 Taf. viii. fig. li. 



Spongy cortical shell with rather comjjact framework, four times as broad as the enclosed 

 medullary shell, the pores of which are irregular, roundish, three to four times as broad as the bars. 

 Two polar spines sword-shaped, two-edged, as long as the shell diameter. 



Dimensio7is. — Diameter of the cortical shell 0-24, medullary shell 0-06 ; length of the spines 

 0-2.5. 



mibitat— Central Pacific, Station 268, depth 2900 fathoms; Thilippine Sea, depth 3300 

 fathoms. 



3. Spongostylus serratus, n. sp. 



Spongy cortical shell with lax framework, ten to twelve times as broad as the enclosed 

 medullary shell, the pores of which -are irregular, I'oundish, once and a half to twice as broad as 

 the bars. Two polar spines longer than the sheU diameter (broken off in the observed specimen), 

 three-sided prismatical, with three straight serrated edges. 



Dimensions. — Diameter of the cortical shell 0-5, medullary shell 0'04 ; length of the spines 

 0'6 or more. 



Habitat. — South Pacific, Station 285, depth 2375 fathoms. 



Genus 59. Siwngostylidium,^ Haeckel, 1881, Prodromus, p. 455. 



Definition. — S t y 1 o s p h £e r i d a witli spongy spherical cortical shell, enclosing two 

 concentric spherical latticed medullary shells, and with two opjiosite, free radial spines. 



The genus Sponyostylidiuni difl'ers from Sp>ongostylus by duplication of the latticed 

 medullary shell, and therefore bears the same relation to it as Spongodictyon to 

 Spongop)legina. 



1. Spongostylidium streptacanthum, n. sp. 



Both meduUaiy shells spherical, with small, regular, circular pores, twice as broad as the bars 

 (outer twice as broad as the inner). Spongy cortical shell enclosing it with dense fi'amework, four 

 times as broad as the outer medullary shell. Two polar spines very large, four times as long as 

 the diameter of the outer shell ; as broad as the inner medullary shell, with three dentated, spirally 

 contorted edges. (Very similar to the common SpoTigosphmra streptacantha and to Hexadoridium 

 stre2:)tacanthum, but with only two opposite spines in one axis.) 



Dimensions. — Diameter of the cortical shell 016, of the oiiter medullary shell 0'04, inner 0"02 ; 

 length of the spines 07 and more, breadth 0'02. 



Habitat. — IncUan Ocean, Cocos Islands, Eabbe. 



1 Spongostylidium, diiiiiiuUive of Spongostylus. 



