Summary of Conclusions Reached 527 



that connected Africa and S. E. Asia in earlier Tertiary 

 time, probably up to the close of Oligocene time. Further 

 migrational continuity from central Africa to Madagascar 

 and India seems equally assured. Such also have often 

 been demanded in the past by biogeographers. 



From evidence already gathered regarding Centrarch- 

 idae, Percidae, Cichlidae, and Pomacentridae on to the 

 Scaridae, it is accepted that a wide Gondwana land bridge 

 stretched from north-east Brazil to western Africa, during 

 Cretaceo-Eocene time. So migration and progressive evolu- 

 tion of freshwater families like Cichlidae, also divergent 

 migration from these or allied groups into marine surround- 

 ings along the north and south shores of this interconti- 

 nental land, gave rise to Pomacentridae and other families. 



Breaking up and disappearance of this land-bridge 

 probably occurred during Oligo-Miocene time, and correla- 

 tive changes in Africa gave rise to the great "eurycolpic" 

 crustal folds and to the extensive lakes that have existed 

 there since Pliocene days. About the same time the Indo- 

 Mascarene bridge was breaking up, and thereafter centres 

 or foci for separate evolution alike of freshwater and of 

 marine forms originated. Detailed consideration is then 

 given to the resulting evolution of the Cichlidae in S. 

 America and in Central Africa. 



Branner's contention is accepted as correct for fish 

 distribution, namely that the existing Antilles were, during 

 the Cretaceous period, parts of a wide connecting land that 

 united N. and S. America. So evolving representatives 

 of the families Percidae, Centrarchidae, Percopsidae, and 

 Aphredoderidae, were enabled to spread southward into 

 the Brazilian "massif" or ArchencheUs of that period, and 

 there to undergo further evolution. 



But while steady evolution, even amid considerable seis- 

 mic, volcanic, and diastrophic change, was proceeding over 

 the above areas of North and South America, the Old 

 World in large part was "evidently shaken to its core by 

 seismic and volcanic action, and had most of its teleostean 

 genera obliterated during the late Cretaceous and early 

 Eocene periods." 



