OPALINID CILIATE INFUSORIANS — METCALF 



607 



Lemuria and Malaysia were united but Australia and Malaysia 

 were not; (2) the development of Bujo in eastern Asia, from some 

 archaic bufonid already having Cepedea; (3) Bufo passed with its 

 Cepedeas via the Cretaceous circum-Pacific land-strip to Ecuador 

 and later it entered North America in the Tertiary when the land- 

 strip fused with western North America, and its southern portion, 

 between North America and South America, became interrupted; 

 (4) either then or a little later Rana with its Opalinas had reached 

 North America by way of Siberia and Alaska and Rana and Bufo 

 each gave the other of their opalinid parasites, Rana giving Opalina 



Figure 157.— Geographic distribution of Bufo. 



to BuJo and Bufo giving Cepedea to Rana; but, the old route to 

 South America being interrupted and the new isthmian route not 

 yet being formed, neither Rana nor Bufo entered South America 

 from the northern continent after their interchange of parasites. 

 The one paleogeographic feature of this hypothesis that is possibly 

 new is the suggestion that there was a brief time between the Jurassic 

 and Cretaceous periods when Lemuria and Asia-Malaysia were united 

 and Asia-Malaysia and Australasia were not. Tlus mvolves only 

 slight modification of conclusions by Arldt and others 



Bufo is a most hospitable host, accepting any opahnids it mee s. 

 It bears all kinds, its most common guests in any region bemg tlie 

 ones most prevalent in that environment. ^..KnKlv dJH 



Bufos, not found in Madagascar and the SeycheUes, Probably d^ 

 not ent;r Africa until the late Tertiary, cx,ming sou th^^^^^ 

 Euro-Asia and reaching Ethiopia by way of the Nile VaUey. {Rarui 

 may have taken the same route at the same time.) 



