RECENT RESEAECIIES ON THE RADIOLAIIIA. 177 



Subdivision i. Haliommatida. 



Two shells only. Genera: Aspidonima, HaJiomma, Tetrapyle, 

 Ileliodiscus, Ommatospyris, Ommatocampe. 



Subdivision ii. Actinommatida. 



Three or more shells. Genera: Actinomma, Didymocyrtis^Cro- 

 myomona, Chilomma. 



Subsection 2. Spongosph^rida. 

 One or more concentric shells, with spongy skeleton annexed. 



Subdivision i. Cladococcida. 



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

 dococcus. 



Subdivision ii. Coelodendrida. 

 Shell with hollow radiant spicula. Genus Ccelodendrum. 



Section IV. ACANTHOMETEIDA. 



Eadiolaria with radial skeleton the radii of which meet in the 

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

 nuclear vesicle ; yellow cells generally absent. 



Subsection 1. Ttpica. 



Eadii devoid of processes diverging from them at right angles, 

 which by their union form a circumferential structure. 



Subdivision i. Acanthostaurida. 



Eadii symmetrical, but only meeting at their apices within the 

 capsule. Genera : AcantJiometra, Xiphacantlia, AmphiloncJie, Acan- 

 tkostaurus, Lithoptera. 



Subdivision ii. AstrolitJiida. 

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

 Astrolithium, StauroUthium. 



Subdivision iii. Litholophida. 

 Eadii unsymmetrical. Genera : LitholophuSj Actinellius. 



Subdivision iv. Aeantkochiasmida. 



Eadii each perforating the capsule twice and adjoining, but not 

 by their apices within the capsule. Genus Acanthochiasma. 



