FOSSIL SPONGES, ETC. 



33 



they do not ; as if, in the former case, their silicated 

 shells had been dissolved, and the silica drained off to 



Fig. 25. — Transverse sections of Foraminifera ill 

 limestone (magnified). 



Fig. 24. — Appearance of 

 fossil Foraminifer in 



Carboniferous limestones ^, , _ . .^ ^ .^ ,v 



(magnified). Fig. 26.-- Fragment of fossil Foramuafer (magnified;* 



Fig. 27. -Radiolarlan (recent). 



