354 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



What I have said will, I believe, make it clear that our present 

 knowledge of the fishes very distinctly favors a late Mesozoic or very 

 early Tertiary South Atlantic land connection and makes a direct 

 northern origin of at least the South American ostariophysans seem 

 exceedingly unlikely. But I refuse to take a definite stand on these 

 questions. It would be extremely presumptious, on the basis of the 

 fishes alone, to attempt a flat contradiction of thcHolarctic dispersal of 

 the mammals, reptiles, and amphibians so ably advocated by Matthew 

 (1915), Noble (1925), and Dunn (1923 and 1931). Our knowledge of 

 fossil fresh-water fishes, especially in South America and Africa, is 

 very meager and I realize how quickly the discovery of critical fossil 

 evidence might change the picture. However, I do beUeve that, 

 fossils aside, the real fresh-water fishes oft'er better, clearer, and vastly 

 more conservative continental zoogeographical evidence than any one 

 of the classes of quadrupeds, and their basic classification is far better 

 understood than that of the frogs and perhaps of the reptiles. The 

 mammals take precedence only because of the more abundant fossil 

 record. My cliief contention is that the proponents of Holarctic 

 dispersal have given too little attention to contrary conclusions in 

 other groups and have, perhaps, ridden along on the coattails of the 

 mammal evidence a little more easily than the evidence of their own 

 groups actually warrants. 



The true explanation of the apparent conflict between the fish and 

 quadruped evidence may lie in a direction that I have not seen pointed 

 out. If the epi-Mesozoic interval were a time of great upUft and 

 denudation, of longer continental duration than generally supposed, it 

 may have been long enough for the dififerentiation of characins and 

 other primitive ostarioph^'^sans in the north, the southward dispersal 

 of a few types of ancestral bagrid-pimelodid catfishes and generalized 

 characins into Africa and South America, and the extinction of these 

 in Holarctica. We do know that much of the record of this period 

 has been lost. But this is pure speculation, and, in the words of 

 Regan, "The * * * view that Ostariophysi originated in the 

 north and spread southwards, involves so many improbabilities as to 

 be almost unbelievable." 



Returning to the North American fishes, it may be said that there is 

 no particular argument about them. They, at least, seem to have 

 originated in the north, either in North America or the often-con- 

 nected Eurasia. The South American ones are a problem, and I 

 leave them thus, up in the air, so to speak, for it will be remembered 

 that I promised to come to no conclusions. 



WEST INDIAN ZOOGEOGRAPHY" 



The geological history of the land and fresh-water vertebrate 

 animals of the West Indies before the Pleistocene is still almost 



" I am entirely incompetent to handle the invertebrate evidence and have not referred to it. 



