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



to ten on the half equator. Medullary shell spherical, one-third as broad as the cortical shell. 

 Polar spines very strong, three-sided pyramidal, as broad at the base as three pores ; the larger 

 about as long as the main axis, the smaller only one-third as long. 



Dimensions. Major axis 012, minor 01; pores O'Ol, bars 0'005 ; medullary shell 0'035; 

 length of the larger polar spine Oil, of the smaller - 04, basal breadth 0'03. 



Habitat. Indian Ocean, Madagascar, surface, Rabbe. 



6. Druppatractus ostracion, n. sp. (PI. 16, figs. 8, 9). 



Cortical shell thick walled, thorny, with regular network. Proportion of the two axes = 4:3. 

 Pores circular, hexagonally framed, three to four times as broad as the crested bars ; from every 

 corner of the hexagon (between three rneshes) arises a short papilla ; the bottom of every funnel- 

 like mesh is closed by a very thin plate with three regular, circular pores (occasionally four), 

 sometimes confluent, at other times separate. Medullary shell (fig. 9) half as large as the 

 cortical, ellipsoidal and papillate, with regular, circular pores. Polar spines very strong, three-sided 

 prismatic, often somewhat irregular, with short apex ; the larger once to twice as long as the 

 main axis, the smaller scarcely half as long. 



Dimensions. Major axis 016, minor 012 ; pores 0'02 (porules at their base O'Ol), bars 

 0-006 ; axes of the medullary shell 0'07 and 0'06, its pores O'Ol, bars 0'003 ; length of the larger 

 polar spine 015 to 0'3, of the smaller 0'07 to 0'09, basal thickness 0'03. 



Habitat. Pacific, central area, Station 265, depth 2900 fathoms. 



7. Druppatractus coronatus, Haeckel. 



Stylosphcera coronata, Ehrenberg, 1872, Abhandl. d. k. Akad.d. Wiss. Berlin, p. 84, Taf. xxv. fig. 4. 



Cortical shell thick walled, thorny, with regular network. Proportion of the two axes = 5:4. 

 Pores circular, simple, twice as broad as the bars ; eight to ten on the half equator. Medullary shell 

 circular, one-third as broad as the cortical shell. Polar spines furrowed and angular ; the longer 

 and thinner pyramidal about as long as the main axis, the shorter and thicker scarcely half as 

 long, thickened towards the short conical apex. 



Dimensions. Major axis 0'08 to 01, minor 0'06 to O'OS ; pores O'Ol, bars O'OOS ; diameter of 

 the medullary shell 0'03 ; length of the large polar spine 0'08 to 012, of the shorter 0'04 

 to 0-05. 



Habitat. Fossil in the Tertiary rocks of Barbados ; also living in the depths of the Pacific, 

 central area, Stations 265 to 268, depth 2700 to 2900 fathoms. 



Subgenus 3. Druppatractona, Haeckel. 



Definition. Network of the cortical shell irregular, with meshes of unequal size or 

 dissimilar form ; surface smooth, without thorns or papillae. 



