Distribution of Primitive Fishes 501 



Seventh: While the evidence is as yet largely negative, 

 it seems that fishes may not have reached the S. Atlantis 

 continent till Triassic or possibly Jurassic times, or if 

 they did we are still ignorant of their nature and time of 

 distribution. If this suggestion is a correct one it might 

 indicate that a considerable seabarrier intervened between 

 North and South Atlantis from the Silurian or Devonian 

 till the Triassic period; or if any connection existed it was 

 of a temporary kind and not helpful for passage of a fresh- 

 water fish fauna. 



Eighth: Great and fundamental continental changes 

 were effected during the late Jurassic and specially during 

 the Cretaceous epoch. Not the least important of these 

 were the formation of a wide bridge from N. to S. America, 

 and the widening even of the Afro— S. Atlantis bridge. 

 During this time many species and genera evolved over N. 

 Atlantis. These sent migrant types of evolved "ganoids," 

 and derivative evolving teleosts southward into Guayano- 

 Brazilian freshwaters on the east, and into Archandea on 

 the west. Later, and during upper Cretaceous to lower 

 Eocene time, the Brazilian groups sent migrant and largely 

 teleostean types across the Afro— S. Atlantis bridge into 

 West and Central Africa; while Lepidosiren and possibly 

 other fishes, — the former probably derived from a common 

 African ancestor with the African Protopterus — travelled 

 westward into Brazil and Paraguay. 



Ninth: During late Jurassic and early Cretaceous times 

 numerous derivative elasmobranch genera, as well as teleo- 

 stean genera, gradually evolved from elasmobranch and 

 "ganoid"ancestors that had all been of freshwater habitat. 

 Some of these migrated into the sea, spread rapidly, and 

 gave rise to the abundant marine teleostean fish-fauna that 

 populated the shores of N. Atlantis up to close of the Cre- 

 taceous at least. Owing to some widely destructive agency 

 or agencies thereafter, the elasmobranch genera were in 

 part obliterated, the teleostean very largely. 



Tenth: During the mid and late Cretaceous, and from 

 then onward through Eocene to early Miocene time, an 

 extensive South Continent arose, that connected on the 

 West with Andean S. America, and extended eastward till 



