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



them short bristle-like radial spines. Polar spines three-sided pyramidal, about as long as 

 the radius of the outer shell, one-third as broad at the base. 



Dimensions. Diameter of the outer shell 015, middle 0'09, inner O05 ; pores of the cortical 

 shell O'Ol, bars 0'005 ; length of the polar spines 0'09, basal breadth 0'03. 



Habitat. North Pacific, Station 244, depth 2900 fathoms. 



Subgenus 3. Amphisphcerissa, Haeckel. 



Definition. Pores of the cortical shell irregular, of different size or form ; surface 

 smooth or a little rough, without spines or thorns. 



6. Amphisphcera cronos, n. sp. (PL 17, fig. 5). 



Eadial proportion of the three spheres = 3:2:1. Cortical shell thin walled, smooth, with 

 irregular, roundish pores, two to four times as broad as the bars; eight 'to ten on the half equator. 

 Outer medullary shell similar, but with pores of half the size, connected with the cortical shell by 

 numerous radial beams ; inner medullary shell with very small pores. Polar spines three-sided 

 pyramidal, as long as the axis of the inner medullary shell, half as broad at the base. 



Dimensions. Diameter of the outer shell 012, middle 0'08, inner OD4 ; pores of the cortical 

 shell O'Ol to 0'02, bars 0'05 ; length of the polar spines 0'04, basal breadth 0'02. 



Habitat. South Atlantic, Station 330, surface. 



7. Amphisphcera pluto, n. sp. (PI. 17, figs. 7, 8). 



Eadial proportion of the three spheres about = 4:2:1 (or 11:7:3). Cortical shell thick 

 walled, smooth, with very irregular, roundish pores, two to four times as broad as the bars ; 

 eight to ten on the half equator ; often two to four pores confluent. Margin of their outer 

 aperture double. Polar spines conical, double contoured, as long as the radius of the outer shell, 

 one-third as broad at the base. 



Dimensions. Diameter of the outer shell Oil, middle shell 0'07, inner shell 0'03 ; pores 

 of the cortical shell O'Ol to 0'02, bars 0'06 ; length of the polar spines 0'06, basal breadth 0'02. 



Habitat. Central Pacific, Station 268, surface. 



Subgenus 4. Amphisphcsromma, Haeckel. 



Definition. Pores of the cortical shell irregular, of different size or form ; surface 

 spiny or thorny. 



8. Amphisphcera mars, n. sp. 



Eadial proportion of the three spheres = 10 : 3 : 2. Cortical shell thin walled, thorny, 

 with irregular, roundish pores, one to three times as broad as the bars ; sixteen to twenty on the 



