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



one pore ; the major spiiie somewhat longer than the diameter of the shell, the minor scarcely one- 

 third or one-half as long. 



Dimensions. — Diameter of the sphere 014, pores O'OOS, bars 0-002 ; length of the major spine 

 0-16 to 018, of the minor O'Oo to O'O?, basal breadth 0-02. 



Habitat. — Indian Ocean, Zanzibar, 2200 fathoms, Pullen. 



4. Xi23hostylus gaUus, ii. sp. 



Pores regular, circular, five times as broad as the bars. Twelve to sixteen pores on the half 

 equator. Surface smooth. Polar spines very unequal ; the major conical spine one and a half to 

 three times as long as the diameter of the sphere ; the minor pommel-shaped, scarcely one-third as 

 long (length of both spines very variable). 



Dimensions. — Diameter of the sphere 013, pores D'Ol, bars 0^002 ; length of the major spine 

 0-2 to 0-4, of the minor O'OS to 0-08. 



Habitat. — Pacific, central area, Station 268,. depth 2900 fathoms. 



5. Xipliostylus alauda, n. sj). (PI. 14, fig. 15). 



Lithomesjnlus alauda, Haefckel, 1881, Prodrom. et Atlas, Joe. cit. 



Pores subregular, circular, three to four times as broad as the bars ; fifteen to eighteen on the 

 half equator. Surface a little rough. Polar spines irregularly conical or pyramidal, scarcely as long 

 as the radius of the sphere ; one spine simple, the other composed of a bunch of four or five spines 

 united at the base. 



Dimensions — Diameter of the sphere Oil, pores O'Ol, bars O'OOo ; length of the polar spines 

 0-03 to 0-05, basal breadth 0-02. 



Habitat. — Pacific, central area. Station 272, depth 2000 fathoms. 



6. Xijjhostylus anhinga, Haeckel. 



Rhdbdolitlds pipa, Bury, 1862, Polycystins of Barbados, pi. iii. fig. 4. 



Pores subregular, circvdar, about tlie same breadth as the bars ; eight to ten on tlie half equator. 

 Surface smooth or a little rough. Polar spines cylindrical, very irregularly curved like S or contorted, 

 the major three to si.x times as long as the diameter of the sphere, the minor scarcely one-fourth as 

 long as the former, at the end truncated. 



Dimensions. — Diameter of the sphere 0'07, pores and bars 0'005 ; length of the major polar 

 spine 0-2 to 01, of the minor 0-06 to O'OO, basal breadth O'Ol. 



Habitat. — Fossil in the Barbados rocks. 



Subgenus 2. Xiphostyletta, Haeckel. 



Definition. — Pores of the spherical shell regular, of nearly equal size and form ; 

 surface thorny or spiny (other than the two large polar spines). 



