REPORT ON THE RADIOLARIA. 199 



two to eight times as broad as the bars. Radial proportion of the three spheres = 1:2:4. Main 

 spines three-sided prismatic, with prominent, often somewhat contorted edges, at the distal end 

 cuspidated ; longer than the radius of the outer shell. 



Dimensions. Diameter of the outer shell 0'15, middle O07, inner 0'035 ; cortical pores 

 O'Ol to 0'03, bars 0'04 ; length of the six spines Oil, basal breadth 0'03. 



Habitat. Mediterranean (Messina), surface ; Canary Islands (Lanzerote); Haeckel. 



24. Hexacontium periplectum, n. sp. 



Cortical shell double, enclosing a simple medullary shell. Radial proportion of the three shells 

 = 1:4:5. Inner cortical shell thick walled, with irregular roundish pores, two to eight times as 

 broad as the bars; five to seven on the radius. Numerous radial spines, arising from it, are 

 connected below their distal ends (at equal distances from the centre) by delicate branched threads, 

 and so form an outer, irregular, thin, cortical shell, with spiny surface. Six main spines three-sided 

 pyramidal, about as long as the radius. 



Dimensions. Diameter of the outer shell 0'22, middle 0'2, inner 0'045 ; cortical pores (of botli 

 outer shells) O'Ol to 0'03, bars O'OOl to 0'005 ; length of the spines 01, basal breadth O02. 



Habitat. North Pacific, Station 241, surface. 



Genus 80. Hexadendron, 1 Haeckel, 1881, Prodromus, p. 452. 



Definition. C u b o s p h se r i cl a with three concentric lattice-spheres and six 

 branched spines of equal size. 



The genus Hexadendron differs from Hexacontium in the ramification of the six 

 dimensive spines, and from the similar Hexancistra in the duplication of the medullary 

 shell. As in the latter instance, each spine can bear either three simple lateral branches 

 or three rows of pinnate lateral branches. 



1 . Hexadendron quadrieuspis, n. sp. 



All three shells spherical, with radial proportion = 1:2:6. Pores of both medullary shells 

 regular circular, twice as broad as the bars. Pores of the cortical shell irregular roundish, four to 

 six times as broad as the bars ; surface a little thorny. Six radial spines prismatic, with three 

 prominent wing-like edges, which are prolonged below the distal end in three curved lateral 

 branches. (Differs from Hexalonclu- quadriatspis, PI. 22, fig. 11, mainly in the double medullary 

 shell.) 



Dimensions. Diameter of the outer shell 015, middle 0'05, inner 0'025 ; length of the spines 

 012, breadth (rOl. 



Ifitlitut. Central Pacific, Station 272, depth 2600 fathoms. 



1 Hrxadeiidron** Shell with six true.- ; iiosyO;*. 



