332 THE VOYAGE OF H.M.S. CHALLENGEE. 



1. Xiphatractus armadillo, n. sp. (PI. 17, fig. 11). 



Cortical shell thick walled, smooth, with regular, circxilar pores, about as broad as the bars ; 

 fifteen to sixteen on the half equator. Polar spines three-sided pyramidal, with thick, prominent 

 edges, of irregular form ; the longer about as long as the main axis, the shorter scarcely one-third 

 as long ; their basal breadth equals the diameter of the inner medullary shell. 



Dimensions. Major axis of the cortical shell 0'13, minor axis O'l, thickness of its wall O'Ol ; 

 pores and bars O'OOS ; main axes of the two medullary shells 0'07 and 0'03 ; length of the major 

 polar spine 0'12, of the minor 0'04, basal thickness 0'04. 



Habitat. Pacific, central area, Station 272, depth 2600 fathoms. 



2. Xiphatractus euphractus, n. sp. 



Cortical shell thick walled, smooth, with regular, circular pores, twice as broad as the bars ; eight 

 to nine on the half equator. Each pore has six to nine excisions (commonly eight), elegantly lobed, 

 flower-like (as in Xiphostylus phasianus, PI. 13, fig. 9). Polar spines strong, angulate ; the major 

 pyramidal, longer than the main axis, the shorter elegantly pommel-like, scarcely one-third as long. 



Dimensions. Major axis 0'15, minor 012 ; pores 0'014, bars 0'007 ; main axes of the two medul- 

 lary shells 0'09 and 0'05 ; length of the larger polar spine O'l 6, of the shorter O'Oo, greatest 

 thickness 0'03. 



Habitat. South Atlantic, Station 332, depth 2200 fathoms. 



Subgenus 2. Xiphatractylis, Haeckel. 



Definition. Network of the cortical shell regular or subregular, with meshes of 

 nearly equal size and similar form; surface thorny or papillose. 



3. Xiphatractus spinulosus, Haeckel. 



Stylosphcera spinulosa, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 84, Taf. xxv. 

 fig. 8. 



Cortical shell thin walled, with spiny surface, and large, regular, circular pores, four times as 

 broad as the bars; seven to eight on the half equator. Spines between the pores of the same size, 

 conical. Polar spines also conical, but much larger; the major about as long as the main axis, the 

 minor scarcely half as long; their basal thickness equals the largest pores. 



Dimensions. Major axis O'l, minor 0'08 ; pores 0'012, bars 0'003; diameter of the spherical 

 Medullary shells 0'06 and 0'03; length of the major polar spine 0'09, of the minor 0'04, basal 

 thickness 0'02. 



Habitat. Fossil in the Tertiary rocks of Barbados. 



