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



Subgenus 1. Rhaphidococcus, Haeckel, 1862, Monogr. d. Radiol., p. 365 



(sensu emandato). 



Definition. Pores of the spherical shell regular or subregular, all of nearly equal 

 size and similar form. Radial spines arising from all the nodal-points of the network. 



1. Acanthosphcera tenuissima, Haeckel. 



Heliosphcera tenuissima, Haeckel, 1862, Monogr. d. RadioL, p. 351, Taf. ix. fig. 2. 



Shell extremely thin walled, eight to ten times as broad as one pore. Meshes or pores regular, 

 hexagonal, with thread-like bars ; five to seven on the radius. At each nodal-point (between every 

 three meshes) arises a bristle-shaped radial spine, as long as the diameter of one pore. 



Dimensions. Diameter of the shell 0'2 to 0'25, of the meshes or pores 0'025 to O03, bars below 

 0-0001 ; length of the spines 0'03. 



Habitat. -Mediterranean (Messina), North Atlantic (Canary Islands). 



2. Acanthosphcera tennis, n. sp. 



Shell very thin walled, about twenty times as broad as one pore. Meshes subregular, hexagonal, 

 with thread-like bars ; twelve to fourteen on the radius. At each nodal-point arises a bristle-shaped 

 radial spine, about as long as the radius. 



Dimensions. Diameter of the shell 0'3 to 0'35, pores 0'015 to Q'018, bars below O'OOl ; length 

 of the spines 012 to 016. 



Habitat. Central Pacific, Stations 266 to 274, depth 2350 to 2925 fathoms. 



3. Acanthosphcera macropora, n. sp. 



Shell thin walled, five to six times as broad as one mesh. Pores regular, circular, hexagonally 

 framed, ten to twelve times as broad as the bars. Eadial spines bristle-shaped, as long as the 

 diameter of one pore, arising from all the nodal-points. 



Dimensions. Diameter of the shell 0'07 to 0'08, pores 0'012, bars O'OOl ; length of the 

 spines 0'012. 



Habitat. Central Pacific, Station 271, surface. 



4. Acanthosphcera micropora, n. sp. 



Shell thick walled, forty to fifty times as broad as one pore. Pores regular, circular, 

 hexagonally framed, half as broad as the bars. Kadial spines bristle-shaped, as long as the radius 

 of the shell, arising from all the nodal-points. 



Dimensions. Diameter of the shell 0'22, pores 0'003, bars 0*006 ; length of the spines 01. 



Habitat. South Pacific, Station 288, surface. 



