KEOENT EESEARCHES ON THE RADIO LAMA. 179 



Subsection 2. ETHMOSPHiERIDA. 



One, or two or three circumferential shells united by radii ; if 

 one, then formed of a delicate network with irregular meshes. 

 Grenera : GyrtidosphcBra, JEthmospJicsra, AracTinospJicBva. 



Subsection 3. Acanthodesmida. 

 Shell consisting of a few irregularly united bands. Grenera : 

 Lithocircus, Zygostephanus, AcantJiodesmia, Plagiacantha, Prisma- 

 tium, Dictyocha. 



Section yi. COLLOZOA. 



Simple or compound Eadiolaria ; if single, then with the ske- 

 leton in the form of circumferential detached spicula only. No 

 nuclear vesicle. 



Subsection 1. Poltcollida. 



Compound Eadiolarians. 



Subdivision i. Sphcerozoida. 

 Skeleton absent, or consisting only of scattered spicula. Genera ; 

 Collozoum, Sphcerozomn, Mliaphidozovm. 



Subdivision ii. CollospJicerida. 



Skeleton a spheroidal perforated shell. Genera: Siphonosphcera, 

 Collosphcera. 



Section VII. VESICULATA. 

 Eadiolaria with a nuclear vesicle. 



Subsection 1. Collida. 



Skeleton wanting, or consisting only of scattered circumferen- 

 tial spicula. Genera : Thalassicolla, Thalassolampe, Aulacantha, 

 Physematium. 



Subsection 2. Sphjeeoidea. 



Vesiculata with one or more concentric extracapsular shells 

 bound together by radii. Genera : Heliosphcera, DiplospTicera ? 



Subsection 3. Aflosph^eida. 



Vesiculata with a complex circumferential skeleton of hollow 

 bars. Genus Aulosphcera. 



Subsection 4. Beaohiata. 



Vesiculata with the extracapsular sarcode pi'olonged into one 

 or more arm-like processes. Genus Myxohrachia, 



