FRESH-WATER FISHES— MYERS 361 



Although ichthyologists have never particularly remarked it, it is a 

 fact that all of the primitive, relict forms of fresh-water fishes that have 

 persisted to modern times are inhabitants of relatively sluggish (and 

 usually large) lowland water systems. The late Professor Eigenmann 

 overlooked this when he journeyed to the Guiana plateau in 1908 to 

 search for possible survivors of the fish fauna of his "Archiguiana" ; 

 he found none. Changes in the physical features of mountain areas 

 are too swift to permit survival of any except fishes that have become 

 peculiarly adapted to life in swift water, and the few relicts of a dying 

 race are not the ones that become adapted to such a hard life. Pene- 

 plaination of a mountain range means the extinction of the highly 

 adapted hill-stream fishes, since (despite Regan's case of the astro- 

 blepids) evolution is not exactly reversible and specialized swift-water 

 fishes could scarcely be expected to revert to a slow-water habitat 

 deficient in oxygen. 



The only instances I know of true relict fishes living in mountainous 

 areas concern species existing in moimtain lakes that have been 

 elevated bodily, or which are part of a once extensive plateau lake or 

 river system, and where the certain draining of the lake in the not far 

 distant geological future will sound the death knell of the relict. An 

 especially good example is seen in the remarkable fish Chaudhuria in 

 the Inle Lake, Burma. 



It may be expected that a considerable proportion of a mainland 

 fish fauna living on land masses (islands) subsequently cut off from a 

 continent will be lowland fishes not particularly well adapted to swift 

 water. If the island were to be partially submerged within a com- 

 paratively short geological period, the lowland fish fauna might be 

 entirely annihilated. This would be all the more likely if the original 

 continental connection had been so low as to permit the entrance only 

 of lowland types and the submergence occurred before these lowland 

 fishes had had time to evolve hiU-stream types. 



We do know that many of the Antilles have experienced con- 

 siderable changes of elevation. Barbados in particular appears to 

 have been very badly treated by orogenic or other forces. If we can 

 believe the evidence of its sedimentary deposits, it sank 6,000 to 

 10,000 feet below the sea between the Eocene and Miocene, and in 

 the Pliocene bobbed up again as an island. Naturally, com-plete 

 subsidence below the sea would destroy the fresh-water fauna, and 

 the Greater Antilles have experienced no such devastating changes 

 of level, but even relatively slight subsidence might have a profound 

 effect on the river fishes. 



In spite of this, I feel confident that had aggressive Ostariophysi 

 ever been able to reach the Greater Antilles, nothing short of almost 

 complete submergence of the larger islands would have entirely 

 destroyed them. Characins and carps in particular would have been 



