THE OPALINID CILIATE INFUSORTANS. 



313 



geographic distribution of the family Biifonidae will be found to 

 be in agreement with an Equatorian origin. 



An origin of this apparently primitive group of species of the 

 genus Protoopalina in Jurassic (fig. 233) or Cretaceous (fig. 234) 



times in South America or in Africa and its Madagascar-India exten- 

 sion ; their spread from Patagonia to Australia by way of Antarctica 

 during the later Cretaceous or the early Tertiary (fig. 236) is a com- 

 plicated hypothesis which is not very probable. Any later origin 

 83103—23 ^21 



