THE OPALIXID CILIATE INFUSORIANS. 



383 



sence from Australasia and southern South America is evidence that 

 they arose north of these Antarctic lands. Their distribution, except 

 for their absence from Madagascar, seems to indicate origin in South 

 Atlantis or its Madagascar-India extension, at some time before the 



early Cretaceous and a spread to Malaysia during the Tertiary. The 

 absence of Coecilians from Madagascar though they are present in 

 Africa seems explicable only on the hypothesis that they were once in 

 Madagascar and have since disappeared. Their strictly tropical 

 distribution suggests that their present occurrence may, however, be 



