HASEMAN, GEOGRAPHICAL DISTRIB VTION IN 80 UTH AMERICA 53 



and hence it would be more like the Amazonian than are the Paraguayan ; 

 but in this case we would compare only one environmental complex which 

 is duplicated in the enormous Amazon Valley. (In cases like Central 

 America, the zoogeographer is concerned more with the ancestral dis- 

 tributed form than with the recent cenogenic modifications of them due 

 to the environment.) 



In the same lists, we find 122 species for the lower Parana, only 64 of 

 which, or 52 per cent, are Paraguayan. If this could be true, then the 

 Paraguayan fishes are more like the Amazonian than the Paranean. This, 

 of course, is to a certain degree quite absurd, because small ocean steamers 

 can sail up the La Plata into the central course of either Eio Paraguay or 

 Eio Parana. In this case, according to the old view, fishes would, in the 

 first place, have to find their way overland from the Amazon Valley to the 

 Paraguay (a distance of about 200 miles separating the typical fauna of 

 the two basins), and then, for some unknown reason, remain in the Alto 

 Eio Paraguay and not venture to swim down the Paraguay into the 

 Parana. 



Professor Eigenmann also states that the Alto Eio Parana had only 31 

 species, but I have often collected more than this in a single day. I col- 

 lected more than 100 species in the region of the Alto Bio Parana and its 

 affluents, and there is no reason to believe that the list was then exhausted. 



The point brought out in the above brief review is that far too little is 

 known about the fishes or any other South American fauna to prove any 

 hypothesis by a numerical comparison of the species found in diverse 

 regions. 



If, for example, we add Cichlasoma bimaculatum and Crenicichla lepi- 

 dota to the Sao Franciscan fauna and Gymnotus carapo, etc., to the coast- 

 wise streams, and if we compare the entire river basin, there can be no 

 doubt that some of the faunal regions, and especially the cause of the 

 differences in their fauna as explained by Professor Eigenmann, do not 

 agree with the actual facts. 



The alleged support derived from the fishes for an Archiplata, Archi- 

 guiana and Archamazonia needs no discussion, because the geological evi- 

 dence shows that no post-Paleozoic seas have invaded the Piano Alto. In 

 the case of Patagonia, there have always been two possible connections 

 with the Piano Alto, one by the Cordova and the other by the Archean 

 rocks of the Andean region. Inasmuch as the invasions of the sea were 

 usually north and south, there is no evidence that southern South America 

 was completely isolated for a long period from the rest of South America 

 by an arm of the sea. 26 



See Pilsbry, 1911. 



