352 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



they were, or a parallel group, now extinct, that possibly arose from 

 the same marine ancestors as the cichlids. Moreover, even if Prwca- 

 cara was a cichlid, it should be remembered that even today this group 

 is not particularly averse to sea water. The genus had for its com- 

 panions in the Green River lake some fishes of marine groups like 

 Diplomystus,'^ gonorhynchids, and rays that frequently come up 

 tropical rivers today. In any event, the Green River shales give us a 

 pretty picture of the early North American fresh-water fauna before 

 the Miocene invasion of carps. 



If the South American fishes did not come from North America, 

 where did they originate? The Ostariophysi in particular certainly 

 had a common origin somewhere. I must confess that I do not know, 

 nor do I believe that anyone can unravel the history of this order 

 without the fossil evidence still locked in pre-Tertiary rocks. With- 

 out this evidence, speculations on the earlier dispersal of the order 

 are useless. Naturally, it can be argued that all we have against the 

 early presence of South American groups in the north is negative 

 evidence, but if the southern families never existed in the north, 

 negative evidence is all wo can expect to find there. Moreover, the 

 Tertiary record of North American fishes is not a blank, and if chara- 

 cins and similar old and aggressive groups were present in North 

 America during any part of the Tertiary, it is exceedingly strange 

 that not a single fossil has come to light. There is every probability 

 that most of the dominant endemic South American ostariophysan 

 families are at least as old as the Eocene, and if they were present 

 in North America at one time, some remnant of them ought to show 

 up in such formations as the Green River. The European and 

 Asiatic fossU evidence of the northern origin of the older African 

 fishes is as nonexistant as the North American. 



Eigenmann, the most eminent student of the South American 

 fishes, believed that there was a very definite pre-Tertiary conti- 

 nental connection between South America and Africa, to account for 

 the similarities plainly seen in the characins, cichlids, nandids, and 

 others, but I cannot accept his gigantic land bridge (or some of his 

 South American paleogeography) without better geological evidence 

 than I have seen. Regan (1922) postulates a somewhat similar 

 bridge. 



One fact alone prevents me from believing in a wide, open, conti- 

 nental connection across the South Atlantic during the life of the 

 present South American and African families of fresh-water fishes. 

 I have mentioned the occurrence in Africa of a most remarkable 

 assemblage of undoubtedly old families of isospondylan teleost fishes, 



" The rough-backed Eocene herrings of the genera Diplomystut and Knighlia have Living marine relatives 

 on the coasts of Chile (Ethmidium) and Australia (Hyperlophui). Diplomystut should not be confused with 

 the Chilean fresh-water Diptomyste*, the most primitive known catfish. 



