174 HISTORICAL GEOLOGY 



able falling off after their culmination in the Mississippian, but 

 in the Mesozoic they regained prominence. 



Aster ozoans of this age have not been found in fossil form, 

 but, judging b3^ their previous and subsequent history, they must 

 have existed. 



Echinoids were much like the Mississippian forms though rare. 



Fig. 102 

 A Cycadofilices or Seed-fern. Restored by D. H. Scott and J. Allen. (From 

 Chamberlin and Salisbury's "Geology," courtesy of Henr}' Holt and 

 Company.) 



Molluscoids. — Bryozoans continued to be common, though 

 the peculiar spiral forms (Archimedes) disappeared. 



Brachiopods were still common but by no means as prominent 

 as in earlier Paleozoic periods. They were much like the Missis- 

 sippian forms. A noteworthy fact was the almost world-wide 

 distribution of some of the species, which indicates either actual 

 land bridges or at least shallow water areas connecting all the 

 continents. 



