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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 87 



If it arose at the eastern end of this Antarctic land-complex, there 

 remains the question whether the place of its evolution was Patagonia 

 or tropical America. Its hosts are leptodactylids, bufonids, hylas, 

 and dendrobatids, predominantly leptodactylids. The bufonids other 

 than Bujo carry Zelleriella, so far as known records go, only in South 

 America. They can be left out of account. Bufo does not occur in 

 Austraha, so it could not have been the host in which Zelleriella 

 wandered westward to Australia. Bufo was apparently not in Pata- 

 gonia at the time of this migration. Bufo probably arose in south- 

 eastern Asia, entered North America, and probably Ecuador also, 



FiGUEE 136. — Geographic distribution of Zelleriella. 



by way of the Cretaceous circum-Pacific land-strip (fig. 143, a). 

 This land-strip became for the most part fused with North America 

 during the Tertiary period (fig. 144, b), but the Isthmus of Panama 

 was not formed until the middle Phocene, and before that time the 

 land-strip had apparently disintegrated, giving no passage between 

 North and South America. Both Bufo and Hyla, but not Zelleriella, 

 were probably in tropical South America before the leptodactylids, 

 with Zelleriella, passed to Australia (see the discussion of the lep- 

 todactylids, p. 600). 



Zelleriella, the dominant opalinid in leptodactylids, apparently 

 evolved in them in Patagonia, or greater Antarctica of which it was 

 a part, before Patagonia and Brazil united (middle Miocene?) (fig. 

 145, a). It passed to Australia, but not to Asia-Malaysia. This 

 migration occurred, therefore, after the Jurassic, probably after the 

 earUest Cretaceous, period, when Austraha and Malaysia were 

 permanently separated. This makes the date of Zelleriella's origin 



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