4o8 Evolution and Distribution of Fishes 



evolution in Madagascar, in North India, and in the Malay 

 region, of purely indigenous species, requires a lapse of 

 time that must have extended from at least late Oligocene 

 days to the present. 



As a biological outcome of such changes, the Cichlidae, 

 Anabantidae, Ophiocephalidae and Osphromenidae became 

 split up from previous geographic continuity into a series 

 of localized groups, the South American, the African, and 

 the South East Asiatic. Of these the central African group 

 is preeminently suggestive. For while the Great Lake and 

 swamp areas must have existed there from at least Eocene 

 times, the extensive faulting above noted gave rise to deep 

 lakes, river valleys, and swamps that became more or less 

 isolated from each other. Most notable of these was the 

 deep but elevated fissure now occupied by Lake Tanganyika 

 to which reference has already been made. 



As Boulenger specially has shown (227) and as Moore 

 has further emphasized (■2^g) many Cichlid genera evolv- 

 ed in or became — amid destructive geologic changes — re- 

 stricted to that Lake. Thus of thirteen known species of 

 Lamprologus, eleven are peculiar to Tanganyika. The 

 three species of Ectodus; the two species of Bathybates, 

 Xenotilapia, Trematocara, T elmatochromis , TropJieus and 

 Petrochromis; the single species of Grammatotria, Gephy- 

 rochromis, Steatocraniis, Asprotilapia, Eretmodus^ Spath- 

 odus, Perissodus, Xenochromis and Plecodiis are all similar- 

 ly endemic. On the other hand Paratilapia with thirty 

 species, and Tilapia with sixty species, are distributed over 

 a large part of Africa from the south central part including 

 Madagascar, northward to Asiatic Syria. Such facts might 

 suggest that these two genera are the most ancient and 

 primitive migrants from eastern South America, and that 

 from them as derivatives the other genera were compara- 

 tively recently evolved. 



In contrast Acara, a genus still surviving, has been 

 described by Woodward from the tertiary of San Paulo, 

 Brazil, while Priscacara is an early Eocene North American 

 genus that is known in several species. Origin of the entire 

 group Cichlidae in North America is therefore fairly well 

 Indicated, with subsequent spread Into South America and 



