RADIOLARIA 259 



Spines more or less uniform in size 



Spicules circular in cross-section Family 1 Acanthometridae 



Genus Acanthometron (Fig. 103, c) 



Spicules cruciform in cross-section Family 2 Acanthoniidae 



Genus Acanthoma (Fig. 103, d) 



Two opposite spines much larger Family 3 Amphilonchidae 



Genus Amphilonche (Fig. 103, e) 



Radial spines few, arranged according to Muller's law; with tangential skele- 

 tons Legion 3 Acanthophractida 



20 radial spines of equal size; shell composed of small plates, each with one 

 pore Family 1 Sphaerocapsidae 



Genus Sphaerocapsa 



Two or six larger spines 



Two enormously large conical sheathed spines. . .Family 2 Diploconidae 



Genus Diploconus 



Six large spines Family 3 Hexalaspidae 



Genus Hexaconus (Fig. 103,/) 

 Suborder 2 Peripylea Hertwig 



Solitary; skeleton wanting or simple spicules; mostly spherical 



Legion 1 Collodaria 



The nucleus spherical with smooth membrane 



With intracapsular vacuoles; with or without spicules 



Family 1 Physematiidae 



Genus Lampoxanthium (Fig. 104, a) 



With extracapsular vacuoles; with or without spicules 



Family 2 ThalassicoUidae 



Genus Thalassicolla (Fig. 104, h) 



The nuclear wall not smooth 



The nuclear wall branching out into pouches; structure similar to the last 

 Family 3 Thalassophysidae 



Genus Thalassophysa 



The nuclear wall crenate 



With a huge double spicule; large forms. .Family 4 Thalassothamnidae 



Genus Thalassothamnus 



With a latticed skeleton with branched and thorny spines 



Family 5 Orosphaeridae 



