OPALmiD CILIATE INFUSORIANS— METCALF 605 



Opalmais in tropical Africa, Madagascar, and India. Rana is in 

 but not abundant in, tropical Africa and is in India and Ceylon but 

 not in Madagascar. This suggests that Opalina evolved in son.e form 

 other than Rana m Lemuria (Indian Oceanland, including Mada- 

 gascar Seychelles Islands, Ceylon, and southern India) after Lemuria 

 and Africa separated in the middle Cretaceous period, and that when 

 It entered Asia proper in the Tertiary, Rana had evolved and was 

 ready to serve as migrating host for Opalina's trip to North America 

 by way of Siberia and Alaska. The absence of Rana and Opalina 



Figure 156.— Geographic distribution of the Dendrobatinae. 



from Australia dates their origin later than the beginning of the 

 Cretaceous. The indication, therefore, is that they arose in the 

 Eastern Hemisphere, in lands north of Australia and separated from 

 it, that is, in Ethiopia-Lemuria during the early Cretaceous. By 

 the middle Tertiary they had a land route to Asia-Malaysia and on to 

 North America, but not to South America. They were too late to 

 catch the Cretaceous circum-Pacific land-strip. Late in the Tertiary 

 there were transient connections with Papua, and Rana took advantage 

 of this, but Opalina and for that matter Cepedea have not been found 

 in Papua. 



Of the Ranidae other than the Raninae: Ceratobatrachns, from the 

 Solomon Islands, seems a late offshoot from the Raninae; the Dendro- 

 batinae (northern Neo tropics) including Mantella (Madagascar) 

 suggest spread across the Atlantic (fig. 156). The Zelleriella parasites 

 of the former are a late adoption from their American neighbors. 

 The OpaUnas of the Madagascar Mantellas were probably adopted 



