REPOET ON THE RADIOLARIA. 393 



polyarthra, exhibits five pairs of chambers on both sides of the meridian plane of the 

 cortical shell, the centre of which includes a double medullary shell. It represents the 

 most simple form of all Zygartida, and may be derived phylogenetically from Cyphonium 

 simply by multiplication of the chambers of the cortical shell, growing on both poles of 

 the main axis. 



Subgenus 1. Ommatocampium. 



Definition. Surface of the cortical shell smooth or rough, without thorns or spines, 

 also without polar spines. 



1. Ommatocampe polyarthra, Ehrenberg. 



Ommatocampe polyarthra, Ehrenberg, 1872, Abhaudl. d. k. Akad. d. Wiss. Berlin, p. 279, 

 Taf. vi. fig. 9. 



Cortical shell with smooth surface, composed of six to ten chambers of the same size and form. 

 Every chamber kidney-shaped, about twice as broad as long, with three transverse rows of 

 circular, subregular pores, twice to three times as broad as the bars. Both medullary shells 

 spherical. 



Dimensions. Length of the six-chambered cortical shell O15 ; greatest breadth of each chamber 

 0'04 ; pores O005 to 0-007, bars 0-002 to 0'003. 



Habitat. California!! Sea, depth 2600 fathoms, Ehrenberg; Pacific, central area, Station 268, 

 depth 2900 fathoms ; fossil in the Tertiary rocks of Barbados, Haeckel. 



2. Ommatocampe increscens, Stohr. 



Ommatocampe increscens, Stohr, 1880, Palseontogr., vol. xxvi. p. 90, Taf. ii. fig. 2, a, b. 



Cortical shell with rough surface, composed of six to ten chambers of nearly the same size and 

 form ; the breadth of the chambers a little increasing towards both poles. Every chamber kidney- 

 shaped, the proximal chambers twice as broad as long, with four or five transverse rows of pores ; 

 the distal chambers three to four times as broad as long, with two or three transverse rows of 

 pores. Form of the pores irregular, roundish, bars between them in the distal part smaller, in the 

 proximal part larger than the pores. Both medullary shells compressed lenticular. 



Dimensions. Length of the six-chambered cortical shell 0'22 ; greatest breadth of the chambers 

 0-09 to 01 ; pores and bars 0'003 to OD06. 



Habitat. Fossil in the Tertiary rocks of Sicily, Grotte, Stohr. 



3. Ommatocampe annulata, n. sp. 



Cortical shell with smooth surface, composed of six to twelve chambers of nearly the same size 

 and form. Each chamber kidney-shaped, twice as broad as long, with four to five transverse rows of 



(ZOOL. CHALL. KXP. PART XL. 1885.) Rr 50 



