RECENT EESEAECHES ON THE EADIOLARIA. 177 



Subdivision i. Haliommatida. 



Two shells only. Genera: Aspidovima, Saliomma, Tetrapyle, 

 Seliodiscus, Ommatospyris, Ommatocampe. 



Subdivision ii. Actinommatida. 



Three or more shells. Grenera : Actinomma, Didymocyrtis, Cro- 

 myomma, Chilomona. 



Subsection 2. Spongosph^eida. 

 One or more concentric shells, with spongy skeleton annexed. 



Subdivision i. Cladococcida. 



Shell with solid radiant spicula. Genera : HhapMdococcus, Cla- 

 dococcus. 



Subdivision ii. Ccelodendrida. 



Shell with hollow radiant spicula. Genus Coelodendrum, 



Section IV. ACANTHOMETEIDA. 



E-adiolaria with radial skeleton the radii of which meet in the 

 centre of the capsule, and consisting more or less of acanthin. 

 No nuclear vesicle ; yellow cells generally absent. 



Subsection 1. Ttpica. 



E-adii devoid of processes diverging from them at right angles, 

 which by their union form a circumferential structure. 



Subdivision i. Acanthostmirida. 



E-adii symmetrical, but only meeting at their apices within the 

 capsule. Genera :. Acanthometra, Xiphacantha, AonphiloncJie, Acan- 

 thostaurus, LitJioptera. 



Subdivision ii. Astrolithida. 

 Eadii symmetrical, but actually united at their apices. Genera : 

 Astrolithium, StauroUthium. 



Subdivision iii. LWiolophida. 

 Eadii unsymmetrical. Genera : Litholoplius, Actinellius. 



Subdivision iv. Aeanthochiasmida. 



Eadii each perforating the capsule twice and adjoining, but not 

 by their apices within the capsule. Genus Acanthochiasma. 



