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



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

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



Dimensions. — Diameter of the outer shell 015, middle 0-09, inner 0-05 ; pores of the cortical 

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



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



Subgenus 3. Ainphisphcerissa, Haeckel. 



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

 smooth or a little rough, without spines or thorns. 



6. AmpliisplicBra cronos, n. sp. (PI. .17, fig. 5). 



Eadial proportion of the three sp)heres = 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 ; imier 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 0-04 ; pores of the cortical 

 shell 0-01 to 0-02, bars 0-05 ; length of the polar spines 0-04, basal breadth 0-02. 



Habitat. — South Atlantic, Station 330, surface. 



7. Amp)hisph(jBra pluto, n. sp. (PI. 17, figs. 7, 8). 



Eadial proi^ortion of the three spheres about=4:2:l (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-tliird as broad at the base. 



Dimensions. — Diameter of the outer shell Oil, middle shell 0-07, inner shell O'OS ; pores 

 of the cortical shell 001 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. AmpjhisphcBromma, Haeckel. 



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

 spiny or thorny. 



8. Amphisphcera mars, n. sp. 



Eadial proportion of tlie 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 



