reproduction; evolution 299 



Cyclocrinus (Fig. 179) is a genus which grew to about seven centi- 

 metres and looked like a miniature golf ball borne on the end of a 

 stalk. Narrow branches arose at the apex of the stalk and each ter- 

 minated in a flattened hexagonal head, but as the edges of adjoining 

 heads were fused together to form the outer membrane, which was 

 only weakly calcified, the cell outlines were clearly visible. Many 

 species are known from the Ordovician and Silurian, all somewhat 

 resembling the living genus Bometella. 



Fig. 180 Dasycladaceae. Primicorallina trentonensis ( x 825). 



(After Hirmer.) 



Primicorallina (Fig. 180), from the Ordovician, had a segmented 

 stem beset with radially arranged branches, each of which branched 

 twice into four branchlets. 



Fig. 181 Dasycladaceae. Diplopora phanerospora ( x 8). 



(After Hirmer.) 



