REPORT ON THE RADIOLARIA. 317 



4. Pnmocarpus melocactus, n. sp. 



Cortical shell thick walled, with irregular, roundish pores, twice to five times as broad as the 

 bars ; eighteen to twenty-four on the lialf equator. Between them arise over the entire surface 

 small conical thorns, not longer than the largest pores. Irregularly scattered over the surface 

 twenty to thirty strong, conical, radial spines, about half as long as the main axis, as broad at the 

 base as a large pore. Both medullary shells ellipsoidal, their main axis identical with that of 

 the cortical shell. 



Diviensions. — Major axis of the outer shell 018, of the middle 0'09, of tlie inner 0-05 ; minor 

 axis of the first 0-14, of the second 0'07, of the third 0'04 ; pores of the cortical shell 0-006 to 

 0-02, bars 0004 ; length of the spines 01, basal breadth 0-01. 



Habitat. — Pacific, central area, Station 268, depth 2900 fathoms ; also fossil in the Tertiary 

 rocks of Sicily; Caltanisetta, Haeckel. 



Geuiis 135. Cromyodrupjya,^ ii. gen. 



Definition. — Druppulida with four or more concentric shells (two medullary 

 and two or more cortical shells), without spines or polar tubes. 



The genus Cromyodruppa is cliaracterised by the multiplication of the concentric 

 fenestrated shell, w'hich is composed of two medullary shells (enclosed in the central cap- 

 sule) and two or more cortical shells (outside it). The former may be either spherical or 

 ellipsoidal. The latter are always ellipsoidal, and in this it differs from Cromyosphcera. 

 Probably Cromyodruppa has arisen from Prnmdum by secondary apposition of more 

 cortical envelopes. 



Subgenus 1. Croniyodruppium, Haeckel. 



Dejinition. — Shell composed of four concentric shells, two medullary and two 

 cortical. 



1. Cromyodruppa cepa, n. sp. 



Shell composed of two ellipsoidal, cortical, and two spherical meduUary shells. Proportion of 

 the mam axes of the four shells = 1:2:4:5. Network of all four shells nearly of the same form, 

 subregular, with circular pores of almost equal size in every shell. The absolute size of the pores 

 increases from the innermost to the outermost shell, but the breadth of the bars does not increase in 

 a similar degree. The bars of the outermost shell are onlj* twice as broad as those of the inner- 

 most ; but the pores are three to four times larger. Surface of all four shells smooth. (The 

 shell greatly resembles that of Cromyatractus tetraphractus, PI. 15, fig. 2, but is devoid of pulur 

 spines ; it differs also in the spherical form of both medullary shells and their relative size.) 



' Cromyodrvppa = Onion-olive ; x^ofivov, Sf !/x5r«. 



