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



Dimensions. — Diameter of the outer shell 012, pores 0-012, bars 0003 ; inner shell 0-04 ; lengtli 

 of the polar spines 0'04, thickness O^OIS. 



Habitat. — Indian Ocean, Cocos Islands, Eabbe. 



10. StiJosphcBra hispida, Ehrenberg, 1854. 



Stylospluera hispida, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 246; 



MikrogeoL, Taf. xxxvi. fig. 26. 

 Haliomma hispidum, Haeckel, 1862, Monogr. d. Eadiol., p. 433. 



Eadial proportion of the two spheres = 3:1. Cortical shell thick walled, spiny, with regidar, 

 circular pores of the same breadth as the bars ; ten to fifteen on the half equator. Polar spines 

 three-sided prismatic, pointed, about as long as the axis of the outer sphere, nearly as broad at the base 

 as the inner sphere. (Compare Sphcerostylus hispidus ; also Ehrenberg, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, 1874, p. 259.) 



I)i7ne7isio)is.^Dia.TXieter of the outer shell 01 to 0-12, pores and bars 0'004 ; inner shell 0'04 ; 

 length of the polar spines 01 to 0'15, basal breadth 0-03. 



Habitat. — Fossil in the Tertiary rocks of Sicily, Barbados, Nicobars, &c. 



11. StijJosplicBra liostylus, Elirenberg, 1875. 



StijlospJicera liostylus, Ehrenberg, Abhandl. d, k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. fig. 3. 



Eadial proportion of the two spheres = 3:1. Cortical shell thick waUed, thorny, with regular, 

 circular pores, three times as broad as the bars ; eight to ten on the half equator. Polar spines 

 conical, once and a half to twice as long as the axis of the outer sphere, half as broad at the 

 base as its radius. (This species, common in the Barbados rocks, is different from Sphcerostylus 

 liostylus, loc. cit., fig. 2, which Ehrenberg beheved identical.) 



Dimemiofis. — Diameter of the outer sheU 01, pores O'Ol, bars 0-0035 ; inner shell 0-03 ; 

 length of the polar spines 0-14 to 0-18, basal breadth 0-02. 



Habitat. — Fossil in the Barbados rocks ; li\-ing in the depths of the ISTorth Atlantic, Gulf 

 Stream, Florida. 



Subgenus 3. Stylosphcerissa, Haeckel. 



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

 fimooth or a little rough, without thorns or spines. 



12. Stylosphcera nana, n. sp. (PI. 16, figs. 12, 13). 



Eadial proportion of the two spheres = 2:1. Cortical shell thick waUed, somewhat irregular, 

 smooth, with irregailar, roundish pores, one to three times as broad as the bars ; eight to ten on the 

 half equator. Polar spines three-sided pyramidal, scarcely as long as the axis of the outer sj)here, 

 and nearly as broad at the base as its radius. (A very variable and irregular form.) 



Dimensions. — Diameter of the outer shell 0-07 to 0-09, pores 0-003 to 0-009, bars 0-003 ; inner 

 shell 0-03 to 0-04 ; length of the polar spines 004 to 0-07, basal breadth 0-03. 



Habitat. — North Pacific, Stations 241 to 253, surface. 



