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



six to eight groups and eighteen to twenty-four pores. Proportion of the' longer axis to the shorter 

 = 6:5. Shorter axis equals twice the diameter of the inner ellipsoidal shell. Polar spines three- 

 sided pyramidal, about as long as the equatorial axis, as broad at the base as a group of pores. 



Dimensions. Major axis of the cortical shell 012, minor axis 01 ; pores 0'004 to 0~012, bars 

 0-003 ; length of the polar spines 01, basal breadth 0'03. 



Habitat. Central area of the Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms. 



Genus 138. Dntppatractus, 1 n. gen. 



Definition. Druppulida with simple ellipsoidal cortical shell and simple 

 medullary shell, with two large opposite polar spines in the main axis of different size 

 or dissimilar form. 



The genus Druppatmctus differs from its near relation Lithatractus in the differ- 

 entiation of the two polar spines, which are different in size or form, often to a very 

 considerable degree. It has therefore the same relation to the latter that Ellipsoxiphus 

 bears to Ellipsostylm. 



Subgenus 1. Druppatractara, Haeckel. 



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

 nearly equal size and similar form ; surface smooth, without thorns or papillae. 



1. Druppatractus ichthydium, n. sp. 



Cortical shell thin walled, with smooth surface and regular network. Proportion of the major 

 axis to the minor = 3:2. Pores circular, hexagonally framed, twice as broad as the bars ; seven to 

 eight on the half equator (as in Xiphostylus alcedo, PI. 13, fig. 4). Medullary shell spherical, 

 one-third as broad as the cortical shell. Polar spines straight, three-sided pyramidal, as broad at the 

 base as one mesh ; the longer equals the main axis of the cortical shell, the shorter only its half. 



Dimensions. Major axis of the ellipsoidal cortical shell 018, minor axis 012; pores O'Ol, bars 

 0'005 ; diameter of the medullary shell 0'04; length of the major polar spine 016 to 0'2, of the 

 minor O'Ol to 012, basal breadth O'Ol. 



Habitat. Mediterranean (Corfu), surface, Haeckel. 



2. Druppactractus hippocampus, n. sp. (PL 16, figs. 10, 11). 

 Stylospheera hippocampus, Haeckel, 1881, Atlas, pi. xvi. figs. 10, 11. 



Cortical shell thick walled, with smooth surface and regular network. Proportion of both axes 

 = 7:6. Pores circular, hexagonally lobed, three times as broad as the bars ; nine to ten on the half 



1 Druppatractus = Spindle-like olive ; 



