Geographic and Geologic Relations 427 



has expressed it thus: "A land connection, whether a land 

 bridge, intermediate continent or land-wave, between the 

 two continents is imperative. This land continent must 

 have existed before the origin of existing genera, and before 

 many of the existing families." 



The distribution of the species of the above two genera 

 aid us fairly well in suggesting the lines of distribution from 

 N. E. Brazil eastward. For 5 species occur in extreme W. 

 Africa that would form the nearest contact point, i is com- 

 mon to N. Africa, Sardinia, and S. Europe, i is peculiar 

 to Spain, I is found from Sierra Leone to the Upper Nile, 

 and 3 are recorded by Boulenger across Africa from Lower 

 Congo to Tanganyika. This would indicate that the en- 

 trant African forms had split into a series that passed 

 northward along a coastal land elevation from Senegal, 

 and entered S. W. Europe by the Gibraltar bridge during 

 late Eocene time. Another series passed, like so many other 

 organisms, eastward across the central African continent, 

 before formation of the great Eastern African Range and 

 the deeper rift valleys. 



A splitting in the migrational journey again took place, 

 so that some attenuate lines passed by the Mozambique- 

 Madagascar and Indian bridge into Ceylon, and ultimately 

 Japan; while another passed, — previous to Pliocene earth 

 shrinkage and rift valley formation — across Abyssinia, 

 North Egypt, and Syria into Persia. Differentiation there- 

 after into isolated species such as now characterize Tangan- 

 yika, Madagascar, Malabar, Spain, and other areas, was 

 slowly effected probably from Pliocene to recent times. 



We now come to several families of bony fishes that 

 indicate origin from some of the most primitive teleosts; 

 that suggest fundamentally similar geographic distribution 

 with each other; and which in geologic relation both con- 

 firm and extend the views already accepted. These are 

 the Hyodontidae, the Osteoglossidae, the Notopteridae, the 

 Mormyridae, the Phractolaemidae, the Pantodontidae, the 

 Symbranchidae, and the collective families of the Apodes. 



Though known only by three living species of Hyodon, 

 that range from the Gulf States to Canada, the first of 

 these families is probably primitive to all of the others. 



