REPORT ON THE RADIOLARIA. 667 



Subgenus 2. Amphitholura, Haeckel. 

 Definition. Surface of the shell with radial spines or thorns. 



3. Amphitholus octacanthus, n. sp. 



Central chamber about twice as high and broad as both cupolas. From the surface arise, 

 symmetrically distributed, eight stout conical radial spines, lying in two diagonal planes, as 

 prolongations of the eight wing-beams, which connect the Tetrapyle-slia^A medullary shell with 

 the two ring-like constrictions of the cortical shell. Pores of the latter regular, circular, twice as 

 broad as the bars ; ten to twelve in the basal semicircle of one cupola. 



Dimensions. Major axis of the shell 015, minor 012 ; pores-0'01, bars 0'005. 



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



4. Amphitholus dodecanthus, n. sp. 



Central chamber a little larger than both cupolas. From the surface arise twelve strong 

 conical radial spines, four on the poles of the major and the minor axis of the shell, lying in the 

 lateral plane; eight others lying in two diagonal planes, as prolongations of the eight wing-beams, 

 which connect the Tetrapyle-shaped medullary shell with the two ring-like constrictions of the 

 cortical shell. Pores of the latter irregular, roundish, twice to four times as broad as the bars ; 

 sixteen to eighteen in the basal semicircle of one cupola. 



Dimensions. Major axis of the shell 015, minor Oil ; pores 0'004 to O'OOS, bars - 002. 



Habitat. North Pacific, Station 256, surface. 



5. Amphitholus acanthometra, n. sp. (PI. 10, figs. 5, 6). 



Central chamber about twice as broad and as high as both cupolas. On the surface quite 

 symmetrically distributed twenty long and strong cylindrical radial spines ; eight in the sagittal 

 plane or in the meridian plane of the central chamber (four opposite in pairs in the principal and 

 the sagittal axes, four others in the middle between the principal and the sagittal spines); four in the 

 horizontal transverse plane, on both sides of the poles of the major or lateral axis ; and eight in 

 diagonal planes (corresponding to the eight wing-spines of Tetrapyle octacantha). In the centre of 

 the central 'chamber is a distinct trizonal medullary shell like that of Tetrapyle, with two vertical 

 columella beams. Pores of the cortical shell subregular, circular, with elevated hexagonal frames, 

 about four times as broad as the bars ; five to seven in the semicircle of one cupola. (This remark- 

 able species differs from Tholartus vicenus in the possession of a medullary shell, from Amphitho- 

 lonium acanthometra by the simple cortical shell. Compare these species). 



Dimensions. Major axis of the shell 014 to 016, minor axis 010 to 012 ; pores O'Olo, bars 

 0'004 ; major axis of the medullary shell 0'04 to - 05, minor (horizontal) axis 0'02 to 0'03 ; length 

 of the twenty radial spines 018 to 0'24, basal breadth O'Ol. 



Habitat. South Pacific, Station 300, depth 1375 fathoms. 



