RADIOLARIA. 23 



pila H., Thalassicolla Huxl. , Thalassophysa H. ; colonial (Polycyttaria) is 

 Collozoum H. 



Fam. 2. Beloidea, skeleton of loose silicious needles. Solitary are Thalasso- 

 sphcera H., Thalassoplancta H., Physematium Meyen ; colonial (Polycyttaria) 

 are Bclonozoum H., Sphcerozoum Meyen. 



Fam. 3. Sphaeroidea, with one to numerous concentric spherical shells. 

 Colonial (Polycyttaria) are Collospkcera Midler one-shelled, Clatkrosphcera H. 

 two concentric shells ; solitary are Stigmosphcera H. 1-shelled, Carposphccra H. 

 2-shelled, Thecosphcera H. 3-shelled, CromyosphoEra H. 4-shelled, Xiphosphcera 

 H. 1-shelled with two radial spines, Stylosphcera H. 2-shelled with two radial 

 spines, Staurosphaera H. 1-shelled with four radial spines. Hexastylus H. one- 

 shelled with six spines, Haliomma H. 2-shelled and numerous spines, Helio- 

 spkcera H. (Fig. 18) with numerous radial spines of two sizes and a fenestrated 

 shell. 



Fam. 4. Prunoidea with ellipsoidal to cylindrical latticed shells and central 

 capsule. Ellipsis H., Druppula H., Sponcjurus H., Artiscus H., Cypliinus H., 

 Panartus H., Zygartus H. 



Fam. 5. Discoidea, shell and central capsule discoidal or lenticular. 

 Ccnodiscus H., Phacodiscus H., Coccodiscus H., Porodiscus H., Polydiscus H., 

 Sponyodiscus H. 



Fam. 6. Larcoidea. 



Order 2. ACANTHAEIA. Skeleton of acanthin, in the form of spines 

 radiating from the central point ; central capsule uniformly perforated 

 (Peripylaria type). 



Fam. 7. Actinelida, with a variable number of usiially irregularly arranged 

 spines. Astrolophus H. , Liiholophus H., Chiastohis H. 



Fam. 8. Acanthonida, with 20 spines arranged according to Midler's law. 

 Acanthomctra J. Miiller (Fig. 17), Astrolonclie H. , Quadrilonchc H., Amphi- 

 lonclie H. 



Fam. 9. Sphaerophracta, with 20 equal quadrangular spines, and a complete 

 fenestrated spherical shell. Sphccrocapsa H., Dorataspis H., Phractaspis H., 

 Phraclopelta H. 



Fam. 10. Prunophracta, with ellipsoidal, lenticular, or double-coned shell, 

 and 20 spines of different size arranged according to Midler's law. Belonaspis 

 H., Hcxulaspis H., Diploconus H. 



Order 3. MONOPYLARIA. Skeleton silicious, rarely without skeleton ; 

 central capsule monaxonic to bilateral, with simple wall and single polar 

 perforated area ; extracapsular plasma without pigment. 



Fam. 11. Nassoidea, without skeleton. Nassela H. 



Fam. 12. Plectoidea. Skeleton of 3 or more spines radiating from one 

 point (placed beneath the basal pole of the c.c. ) or from a central rod; a 

 complete latticed shell is never formed. Plagoniscus H., Plagonium H., 

 Plectanium H. 



Fam. 13. Stephoidea. Skeleton of one to several fused rings, which may be 

 connected by a loose network. Lithocircus H., Zygocircus H., Cortina H. , 

 Stephanium H., Semantis H., Coronidium H., Tympanidium H. 



Fam. 14. Spyroidea. Fam. 15. Botryoidea. 



Fam. 16. Cyrtoidea. Eucyrtidium H. (Fig. 19), helmet-shaped latticed 

 shell outside central capsule, Eucccryphalus H. 



Order 4. TRIPYLAEIA (PH-EODARIA). Central capsule with double mem- 

 brane, at one pole with a spout-like main opening on a striped field, and 



