FOSSIL FORMS 



271 



whorls of branches that arose in groups of four, each bearing 

 secondary branches which terminated in hairs. In the older thalli 

 the outer part of the branch dropped off leaving a scar on the 

 calcareous shell. The sporangia are reported to have been modified 

 branches. Diplopora is a widespread genus from the Triassic rocks 

 of the eastern Alps, Germany and Siberia. 



Fig. 174. Dasycladaceae. Diplopora phanero- 

 spora ( X 8). (After Hirmer.) 



Fig. 173. Dasycladaceae. Primi- 

 corallina trentonensis ( x 8*25). 

 (After Hirmer.) 



Palaeodasycladus (fig. 175), from the Lower Jurassic, bears a 

 resemblance to the living species of Dasycladus. Near the base 

 there were only primary branches, whilst higher up secondary and 

 tertiary branches were to be found. 



Fossil forms, practically identical with living species of Cyjuopolia, 

 Neomeris and Acicularia have been found in all the recent strata 

 from the Eocene upwards. 



