228 



HISTORICAL GEOLOGY 



Angiosperms are reported to have been represented by the 

 Monocotyledons, though the evidence is not veiy conclusive. 



Protozoans. — Foraminifers and Radiolarians were both very 

 abundant and highly diversified. Foraminifers are particularly 



Fig. 137 

 Jurassic Cycad leaves. (After Ward, U. S. Geological Survey, Monograph 48.) 



numerous in certain Jurassic clays, while certain other beds of 

 chert or jasper are almost wholly made up of Radiolarian shells. 



Porifers. — Sponges were very abundant and diversified. They 

 are often beautifully preserved, even to the minutest details. 



Ccelenterates. — Anthozoans (Corals) continued to be com- 

 mon, and all were of the modern Hexacoralla types. 



