32 Dr. E, C. A^. van Hoepen 



into equatorial fresh waters, while their sea-Hving representatives 

 have since become extinct. 



I am only aware of a few plants which might be used to 

 prove transatlantic connections. The Proteaceae occur in South 

 and Centra! Africa, South America, Australia and tropical Asia. 

 If their distribution can only be explained by land bridges, then 

 the four continents must have been united. On the other hand 

 it is quite probable that the Proteaceae had formerly a much 

 larger distribution, which would account for their present occur- 

 rence. Their occurrence in New Zealand, New Caledonia and 

 Madagascar suggests means of crossing ocean barriers. 



The genus Parkinsonia might be called upon to prove some 

 land connection. One species only occurs in South Africa, 

 another only in Mexico, a third in Mexico and California, while 

 a fourth and only other species occurs in the tropics and sub- 

 tropics of the old and new world. This might be explained by 

 a dispersal from the north. There is also a possibility of a 

 phylogenetic explanation, but as long as botanists do not tell us 

 v/hich of the species is the most primitive, this will have to be left 

 alone. 



It will, therefore, be seen that there is no necessity whatever 

 for a land bridge connecting Africa and Brazil and on top of 

 this there is grave biological objection. A land bridge would 

 have enabled whole faunae and florae to migrate. Instead of 

 one or two genera the two regions would show hundreds and 

 hundreds of identical genera and even identical species. There 

 would be numerous genera typical to the two continents, whicli 

 would not show a connection through the northern hemisphere. 

 Where are these faunae and florae? They are not there, because 

 the land bridge never existed. There is one difficulty connected 

 with the Hystricidae. However, where an eminent authority like 

 Dr. W. D. Matthew cannot offer an explanation covering all 

 facts, I shall leave the problem alone. I feel certain that the 

 problem is of a biological nature. A land bridge between 

 Africa and America would not solve it. The land bndges be 

 tween Madagascar, India and Africa, which have been deemed 

 necessary to explain the occurrence of certain mammaJs and 

 birds on the island are also based on inadequate grounds The 



