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PROF. ST. GEORGE MIVART OK 



quite irregularly disposed, but which generally form an external 

 perforated shell with an internal partition or spheroidal mass 

 forming a series of mutually communicating chambers, which are 

 either concentrically or spirally arranged : no flagellum ; growth 

 multipolar or centrifugal ; no nuclear vesicle. 



Subsection 1. Coccodiscida. 



One or more concentric shells included within the internal 

 shell. Genera : Coccodiscus, LithocycUa, Btylocyclia, Astromma, 

 Hymeniastrum . 



Subsection 2. Trematodiscida. 



Central chamber not different from the other and concentric 

 chambers. G-enera : Trematodiscus, Perichlamydium, Stylodictya, 

 Bhopalastrwn, StepJianastrum, Histiastrum. 



Subsection 3. Discospirida. 



Central chamber not different from the other and spirally ar- 

 ranged chambers. Genera : Discospira, Stylospira^ Stylospongia. 



Subsection 4. Lithelida. 



Skeleton spheroidal, with the interior containing a mass of 

 spirally arranged chambers. Lithelius. 



Subsection 5. Sponghda. 



Skeleton with its chambers not separated off, the radial and cir- 

 cumferential elements being irregularly scattered, except that 

 there are often radiating spines. Genera : Spongodiscus, Spongo- 

 trochus, Spongurus. 



Section II. TLAGELLIFERA. 



Radiolaria with a flagellum. No nuclear vesicle. Genera: 

 Spongocyclia, Spongoastericus^ Euchitonia. 



Section III. ENTOSPH^EIDA. 



Eadiolaria with an intracapsular spheroidal shell ; not traversed 

 by radii. No nuclear vesicle. 



Subsection 1. Ommatida. 



Two or three, or more, concentric spheroidal shells. No spongy 

 skeleton. 



