REPORT ON THE RADIOLARIA. 1557 



9. Mesocena octogona, Ehrenberg. 



Mesocena octogona, Ehrenberg, 1841, AbhandL d. k. Akad. d. Wiss. Berlin, p. 417, Taf. i., 

 Nr. iii. fig. 27. 



? Mesocena heptagona, Ehrenberg, 1841, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 417, Taf. i, 



Nr. iii. fig. 26. 



1 Mesocena heptagona, Ehrenberg, 1854, Mikrogeol., Taf. xx. fig. 49. 



1 Mesocena octoradiata, Ehrenberg, 1872, AbhandL d. k. Akad. d. Wiss. Berlin, pp. 163, 273. 

 1 Mesocena nonaria, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, pp. 163, 273. 



Kings regular, octogonal, with eight radial spines on the eight corners of the ring (sometimes 

 between the common octoradiate rings single rings with seven or nine teeth are intermingled in one 

 and the same calymrna). 



Dimensions. Diameter of the rings O02, length of the spines 0005. 



Habitat. Tropical Pacific; Peru, Ehrenberg ; Station 272 to 274, surface. 



10. Mesocena bisoctona, Ehrenberg. 



Mesocena bisoctona, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 78; 



Mikrogeol., Taf. xxxv., Nr. xviii. figs. 9, 10. 

 Mesocena binonaria, Ehrenberg, 1845, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 78, 



loc. cit. 



Pangs circular, with sixteen teeth ; eight stronger teeth regularly disposed on the outer margin, 

 alternating with these eight smaller teeth on the inner margin. 



Dimensions. Diameter of the rings 0'02, length of the outer spines O'OOS. 

 Habitat. Fossil in Guano from Peru and South Africa, also in Barbados. 



11. Mesocena stellata, n. sp. (PL 101, fig. 9). 



Eings circular, with sixteen teeth regularly disposed on the outer margin of the rings, eight 

 stronger teeth alternating with eight smaller. 



Dimensions. Diameter of the rings O'OS, length of the larger spines O'Ol. 

 Habitat. Central area of the Pacific, Station 270, depth 2925 fathoms. 



Genus 662. Dictyocha, 1 Ehrenberg, 1838, Monatsber. d. k. preuss. Akad. d. 



Wiss. Berlin, p. 128. 



Definition. C annorrhaphida with a skeleton composed of annular pieces, 

 which are fenestrated by one or more arches, arising on one side of the simple ring, but do 

 not form a truncated pyramid (therefore no apical ring). 



The genus Dictyocha is a very remarkable and interesting form of PH^EODAKIA, which 

 has had a curious history. Ehrenberg, who first observed single pieces of it fossil in 

 Tertiary rocks, supposed it to be the siliceous carapace of a Diatom, and gave it the following 



1 Dictyocha = Net-possessing; S/XTUOK, t-^u. 



