332 THE VOYAGE OF H.M.8. CHALLENGEE. 



1. Xiphatractus armadillo, n. sp. (PL 17, tig. 11). 



Cortical sliell thick walled, smootli, with regular, circular pores, about as broad as the bars ; 

 fifteen to sixteen on the half equator. Polar spines three-sided pyramidal, with tliick, 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 0"1, thickness of its wall O'Ol ; 

 pores and bars 0"005 ; main axes of the two medullary shells 007 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. Xijjhatirietus euphractus, n. sp. 



Cortical shell thick walled, smooth, with regular, circular pores, twice as bioad as the liars ; eight 

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

 fiower-Uke (as in Xiplwstylus phasianus, PI. 13, fig. 9). Polar spines strong, angulate ; tlie major 

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



Dimensions. — Major axis 0'15, minor 0'12 ; pores 0-014, liars 0'007 ; main axes of the two medul- 

 lary shells 0'09 and 0'05 ; length of the larger polar spine 0'1('>, of the shorter 0-05, greatest 

 thickness 0"03. 



Habitat. — South Atlantic, Station 332, depth 2200 fatlioms. 



Subgenus 2. Xiphatractylls, Haeckel. 



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

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



3. Xijjhatracttts spinulosus, Haeckel. 



Stylosphcera spinulosa, Ehrenberg, 1875, Abbiuidl. d. k. Akad. «l Wiss. Berlin, ]). 8-t, Taf. xxv. 

 fig. 8. 



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

 broad as tlie 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 0-0:!; length of the major polar spine 0-09, of tlie minor 0-04, basal 

 thickness 0-02. 



Habitat. — Fossil in the Tertiary rocks of Barbados. 



