296 BULLETIN 120, UXITED STATES NATIONAL MUSEUM. 



The data in the host-parasite table are significant from several 

 points of view and need to be classified and scrutinized in a number \ 

 of different ways. One of the things of chief interest will be the 

 geographic distribution. In the discussion of this subject no attempt 

 will be made to treat the data critically from the point of view of 

 geology. The endeavor will rather be to present the known data 

 from the Anura and the Opalinidae and note their implications. 

 Even very scant data, insufficient to have any real weight as they 

 stand, will be stated and their implications noted, with the thought 

 that even very minor items, of slight moment by themselves, may 

 sometime be correlated with other data and then be of interest. The 

 endeavor is, therefore, to have the treatment of this theme inclusive 

 rather than critical. 



In such zoogeographical discussion we need a series of paleogeo- 

 graphic charts for reference, and for this purpose I have chosen 

 to follow chiefly Arldt (1907), who draws his conclusions largely 

 from zoogeographic and phytogeographic data rather than from 

 geologic data alone (figs. 232 and 238). Arldt's liberality in ac- 

 cepting biogeographic data at their face value makes his charts the 

 more useful for our present purpose, which is to give freely, rather 

 than critically, the data and indications from our knowledge of the 

 present distribution of Anura and Opalinidae. Modifying Arldt's 

 charts in several points, we will accept them for reference, and thus 

 free our discussion from the necessity of constantly referring to diver- 

 gent opinions and discrepant data in the fields of geology and bio- 

 geography. 



Arldt's charts have, however, been modified extensively, especially 

 as to South America and its connections. In the Jurassic, Arldt 

 shows all South America united by a broad trans-Atlantic bridge 

 with Africa (fig. 233, A). We show (fig. 233) central South America 

 occupied by ocean, while the highlands of the Guianas and eastern 

 Brazil are united, the Amazon River not having developed as yet. 

 This northeastern land mass is shown united to northern Africa by 

 a mid- Atlantic bridge. Patagonia, Argentina, and southern Chile, 

 distinct from all other South American lands, form a land mass 

 united to southern Africa by a south Atlantic bridge (von Ihering's 

 Archiplata). These two trans-Atlantic bridges are drawn to follow 

 the course of the shallows (1,000 to 2,000 fathoms) in the Atlantic 

 ocean. 



By the time of the early Cretaceous (fig. 234) northwestern 

 South America is shown as connected with westernmost North Amer- 

 ica and Asia by a strip of land in the eastern Pacific, uniting Ecuador, 

 the Galapagos Islands, the mountain region of middle Central 

 A.merica, the tip of the peninsula of Lower California, the islands 



