REPORT ON THE RADIOLARIA 687 



3. Zoniscus tetracanthus, n. sp. (PI. 50, fig. 10). 



Cortical shell nearly quadrangular, one and a half times as long as broad, with four prominent 

 corners, from which arise in the lateral plane four strong, three-sided pyramidal radial spines 

 (opposite in pairs in two crossed diagonal axes). Surface thorny, with exception of the concave 

 lateral sides. Sagittal constriction two and a half times as long as the hexagonal medullary shell. 

 Both equatorial cupolas scarcely half as large as the four corner cupolas. 



Dimensions. Length of the cortical shell 018, breadth 012 ; length of the medullary shell 

 0-07, breadth 0'04. 



Habitat. Pacific, central area, Station 271, depth 2425 fathoms. 



4. Zoniscus octacanthus, n. sp. 



Cortical shell nearly four-sided, prismatic, one and a third times as long as broad, with 

 spiny surface. Eight longer thin radial spines opposite in pairs in two crossed diagonal planes 

 (as in Tetrapyle octacantha). Sagittal constriction two and a half tunes as long as the hexagonal 

 medullary shell. Both equatorial cupolas somewhat larger than the four corner cupolas. 



Dimensions. Length of the cortical shell 016, breadth 012; length of the medullary shell 

 0-055, breadth 0'04. 



Habitat. Pacific, central area, Station 263, depth 2650 fathoms 



5. Zoniscus hexatholius, n. sp. (PL 50, fig. 11). 



Cortical shell nearly rectangular, with four rounded corners and deep sagittal constriction, one 

 and a fourth times as long as broad, with thorny surface. Twelve longer edged radial spines ; eight 

 opposite in pairs in two crossed diagonal planes (as in the foregoing species), four others in 

 the lateral plane, opposite in pairs on both sides of the sagittal constriction, which is scarcely 

 twice as long as the hexagonal, in the equatorial plane constricted medullary shell. Both 

 equatorial cupolas nearly of the same size as the four corner cupolas. 



Dimensions. Length of the cortical shell 016, breadth 013 ; length of the medullary shell 

 0-07, breadth 0'04. 



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



Genus 303. Zonidium* n. gen. 



Definition. Z o n a r i d a with eight dome-shaped chambers of the cortical shell, 

 separated by four annular constrictions (one sagittal, one transverse, and two others 

 parallel to the latter). 



The genus Zonidium must be regarded as a Zonarium, in which the four cupolas 

 (in the quadrants of the lateral plane) are halved by diagonal beams or latticed septa, 



= Little girdle ; ^avKiai/. 



