REPORT ON THE RADIOLARIA. 375 



Subgenus 2. Cannartidissa, Haeckel. 



Definition. Surface of the cortical shell with conical fenestrated protuberances in the 

 greatest breadth of both chambers. 



5. Cannartidium mammiferum, n. sp. (PL 39, fig. 16). 



Cortical shell thin walled, having a circle of six to eight conical protuberances in the greatest 

 breadth of both chambers, each of which exhibits a central apical pore, surrounded by a circle 

 of six to eight oblique larger pores. Between the protuberances occur nine to ten pores on the half 

 meridian of each chamber, circular, subregular, twice to three times as broad as the bars. Polar 

 tubes cylindrical, conical at the closed end, with smaller pores, about as long as the greatest 

 breadth of the chambers, as broad as the spherical outer medullary shell. 



Dimensions. Main axis (without tubes) 013, greatest breadth (including the protuberances) 

 01 ; pores 0'005 to O'OOS, bars 0'003 ; length of the polar tubes 0'09, basal thickness 0'02. 



Habitat. Pacific, central area, Station 268, depth 2900 fathoms. 



6. Cannartidium mastophorum, n. sp. (PI. 39, fig. 17). 



Cortical shell thin walled, of the same form and structure as in the foregoing species, differs 

 from this mainly in the form of the polar tubes, which are not cylindrical, but conical, tapering 

 gradually from the base towards the closed apex. Besides this, the conical protuberances (six in 

 the greatest periphery of each chamber) are more regular and acute, with smaller and more 

 numerous pores. Both medullary shells are here also spherical. 



Dimensions. Main axis (without tubes) 014, greatest breadth (including the protuberances) 

 013 ; pores 0'006 to 0'009, bars 0'004; length of the polar tubes 0'07, basal thickness 0'03. 



Habitat. Pacific, central area, Station 266, depth 2750 fathoms. 



Family XVI. PANARTIDA, Haeckel (PI. 40, figs. 1-9). 



Definition. P runoidea with a four-jointed cortical shell, the external shell being 

 divided by three parallel transverse constrictions into four chambers, in the centre enclosing 

 two internal concentric shells (medullary shells). Central capsule cylindrical, commonly 

 four-jointed (with three transverse annular constrictions). 



The family Panartida (PL 40, figs. 1-9) is characterised by its four-jointed 

 cortical shell, constantly composed of four chambers, lying one behind another in the 

 elongated main axis. They are separated by three ring-like constrictions lying in three 

 parallel transverse planes ; the middle of these is the equatorial plane. In the centre of 

 this latter lies constantly a double medullary shell. 



The Panartida must be derived from the Cyphinida by further increase in the 

 longitudinal or main axis, and by repetition of the equatorial constriction in two 

 transverse planes parallel to it and at an equal distance from it. 



