REPORT ON THE RADIOLARIA. 61 



Subfamily ExHMOSPH^RiDA, 1 Haeckel, 1862, Monogr. d. Kadiol., p. 348 



(sensu restricto). 



Definition. L iosphserida with one single spherical lattice-shell ; living 

 solitary, not aggregated in colonies. 



Genus 15. Cenosphcera? Ehrenberg, 1854, Monatsber. d. k. preuss. 

 Akad. d. Wiss. Berlin, p. 237. 



Definition. L iosphserida with one single latticed sphere, with simple shell- 

 pores (not prolonged into free tubuli) and with simple shell-cavity (without internal 

 radial beams). 



The genus Cenosphcera is the most simple form of all S p h se r o i d e a, and may be 

 regarded as the common ancestral form of this order. The siliceous latticed shell, in 

 which the central capsule is enclosed, represents a simple regular sphere, with simple 

 cavity. The pores of the shell-wall are simple, not prolonged into radial tubuli (as 

 in Ethmosphcera and Sethosphcera). According to the different form of the pores, the 

 numerous species of this genus can be disposed in four different subgenera. Some 

 species may be easily confounded with isolated shells of the corresponding social 

 Collosphcera ; but in this latter the spherical shell-form is commonly more or less 

 irregular, in Cenosphcera quite regular. 



Subgenus 1. Phormosphcera, Haeckel, 1881, Prodromus, p. 448. 



Definition. Pores of the shell regular or subregular, hexagonal or circular, with 

 hexagonal frames or lobes ; all nearly of equal size and form. 



1. Cenosphcera primordialis, n. sp. 



Shell very thin walled, smooth. Pores hexagonal, regular, or subregular ; twelve to fifteen on 

 the half meridian of the shell ; bars between them extremely delicate (only visible when three 

 hundred or four hundred times enlarged). Diameter of the shell nine to ten times that of the 

 meshes. This species is remarkable for the extreme delicacy of the arachnoidal network of the 

 simple spherical shell ; it may be regarded as the common ancestral form of all S p h ae r o i d e a. 

 The shell equals that of Heliosphcera tenuissima (figured in my Monograph, 1862, pi. ix. fig. 2), but 

 differs from it by the smooth surface and the absence of all spines or thorns. I observed this 

 species living in the Indian Ocean, near Ceylon, in 1882; the spherical diameter of the central 

 capsule is about one-third of that of the shell ; the contents of the central capsule are colourless 



1 Ethmosphaerida = Liosphscrida simplicia = Monospha'rida auacantha. 



2 Cenosphtera = Hollow sphere ; K.II/O;, <r#<(>. 



