ORDER III 



EADIOLARIA 



41 



Cretaceous, Textularia, Botalia, Cristellaria, Glohigerina, Miliola and coccoliths are 

 essential constituents of the White Chalk. Individual beds of the Maestricht 

 Chalk consist almost entirely of Calcarina remains ; in the Urgo-Aptian Orhi- 

 tolina is the chief rock-builder ; in the Upper Cretaceous Alveolina. 



The maximum development of the Foraminifera occurs in the Tertiary 

 period. Massive beds of the Eocene Calcaire Grossier of the Paris basin and 

 in the Pyrenees are composed of Miliolidae remains ; other Eocene limestones 

 consist of Alveolina, Operculina, Orhitolites and OrUtoides aggregations. But of 

 far greater geological importance are the NummuUtes, which occur in incredible 

 abundance in the Eocene and Oligocene Nummulites-formations of the Medi- 

 terranean district, Asia Minor and Eastern Asia. 



During the late Tertiaiy the NummuUtes almost entirely disappear ; only 

 Amphistegina continues as an occasional rock-builder, and from the middle 

 and later Tertiary on, the Foraminifera fauna remains very nearly the same 

 as now. 



Table showing Geological Eange of the Foraminifera 



[Tlie foregoing chapter on Foraminifera has been revised for the present work by Dr. 

 Joseph A. Ciishiiian of the Boston Society of Natural History, Boston, Mass. — Editor.] 



Order 3. RADIOL ARIA Muller.^ 



{Fohjcystina Ehrenberg. ) 



Marine Bhizopoda emitting fine, filiform, radially directed pseudopodia, tvith 

 central capsule and extra- cap sidum, and usually with delicate siliceous skeleton. 



The sarcode body of the Radiolarians is differentiated into (1) an inner 

 central sphere or capsule of tough gelatinous-like protoplasm containing one or 



^ Literature : Ehrenberg, O., Mikrogeologie, 1854 ; also memoirs on Radiolaria from Barbados, 

 in Abhandl. Akad. Wiss. Berlin, 1872, 1875.— HaecM, E., Die Radiolarien, 1862.— /c^ewt, Report 

 on tile Radiolaria, in Scient. Results Challenger Exped., Zool., vol. xviii., 1887.^ — Hertwig, R., Der 



