RADIOLARIA 



371 



Genus Actinelius (Fig. 168, a) 

 10-16 spines irregularly set Family 2 Acanthociasmidae 



Genus Acanthociasma (Fig. 168, b) 



Radial spines, few, arranged according to Miiller's law 



Without tangential skeletons Legion 2 Acanthometrida 



Spines more or less uniform in size 



Spicules circular in cross-section . . . Family 1 Acanthometridae 



Genus Acanthometron (Fig. 168, c) 

 Spicules cruciform in cross-section. . . .Family 2 Acanthoniidae 



Genus Acanthoma (Fig. 168, d) 

 2 opposite spines much larger Family 3 Amphilonchidae 



Genus Amphilonche (Fig. 168, e) 



With tangential skeletons Legion 3 Acanthophractida 



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

 with one pore Family 1 Sphaerocapsidae 



Genus Sphaerocapsa 



2 or 6 larger spines 



2 enormously large conical sheathed spines 



Family 2 Diploconidae 



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Fig. 168. a, Actinelius priniordialis, X25 (Haeckel); b, Acanthoci- 

 asma ylanum, X65 (Mielck); c, Acanthotnetron elasticum (Hertwig); 

 d, Acanthoma tetracopa, X40 (Schewiakoff) ; e, Amphilonche hydro- 

 metrica, Xl30 (Haeckel); f, Hexaconus serratus, XlOO (Haeckel). 

 (From Kiihn.) 



