1594 THE VOYAGE OF H.M.S. CHALLENGER. 



1. Orona maxima, n. sp. (PI. 107, fig. 5). 



Shell spherical, with very irregular polygonal meshes. Bars of the loose network smooth or 

 slightly spinulate, very thick, with a pinnulate axial canal. 



Dimensions. Diameter of the sphere 5'0 to 5'5, of the meshes 0'2 to 0'4, of the bars O'Ol. 

 Habitat. Central Pacific, Station 265, depth 2900. 



2. Orona robusta, n. sp. 



Shell spherical, with irregular quadrangular meshes (intermingled with single triangular, 

 pentagonal, and hexagonal meshes). Bars of the coarse network very thick, spinulate. 

 Dimensions. Diameter of the sphere 3'0 to 3'6, of the meshes 0'05, of the bars 0'012. 

 Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



3. Orona crassissima, n. sp. (PI. 107, fig. 7). 



Shell ellipsoidal, slightly prolonged in the main axis, with irregular polygonal meshes of very 

 different sizes and unequal forms. Bars of the coarse network very thick, thorny and dimpled, their 

 surface being covered with a network of prominent polygonal crests. 



Dimensions. Diameter of the sphere 3'0 to 4'0, of the meshes 0'2 to - 5, of the bars 0'02 

 to 0-06. 



Habitat. South Pacific, Station 289, depth 2550 fathoms. 



Genus 672. Orosphcera, 1 n. gen. 



Definition. rosphserida with a simple, spherical (sometimes slightly ellip- 

 soidal or polyhedral) lattice-shell without pyramidal elevations, but with numerous 

 radial spines. 



The genus Orosphcera differs from the preceding Orona, its ancestral form, in the 

 development of simple or branched radial spines. It bears, therefore, the same relation 

 to the latter that Acanthosphcera has to Cenosphcera. In the two latter genera, 

 however, the bars of the network are solid, in the two former hollow. The species 

 referred to Orosphcera are closely allied and require a further accurate examination. 



Subgenus 1. Oronium, HaeckeL 



Definition. Radial spines simple, smooth or spiny, but neither branched nor 

 arborescent. 



1 Orospli<cra = Sphere with hilly elevations; ojoj, 



