348 ORTM ANN— DISTRIBUTION OF DECAPODS [April 3, 



It seems that part of the freshwater Decapods (the identical spe- 

 cies) found their way from Central America to the Greater Antilles 

 during the Pleistocene connection, while the genus Epilcbocera 

 reached the same parts in much older times, in the beginning of 

 the Eocene or even at the end of the Cretaceous. How all these 

 forms were able to get into Central America we shall discuss 

 below. 



To which of the two immigrations Cambarus cubensis belongs 

 remains doubtful. I am inclined to classify it with the older 

 (Eocene) immigration. 



The freshwater crab of the Windward Islands, Potamocarcinus 

 dentatus, confirms the view of Simpson that these islands and their 

 fauna have little to do with the Greater Antilles, but rather that 

 they are related to South America. But, while Simpson believes 

 that the (late Tertiary) population of the Lesser Antilles was ac- 

 complished by drift, I believe that a land connection is indicated. 



7. CONNECTION OF SOUTH AMERICA AND AFRICA. 



The presence of freshwater crabs belonging to the family of the 

 Potamonidce in the Old World (subfamilies Potamoninx and Deck- 

 cniince)., as well as in the tropical parts of the New World (subfamily 

 Potamocarcinince) , has led us above (p. 310) to the assumption that 

 there was once a land connection between South America and the 

 West Indies on the one side and Africa on the other. Similar 

 zoogeographical facts have been emphasized chiefly by von Ihering 

 11891, p. 438, and 1894, p. 406), and, according to him, "all 

 affinities of the freshwater fauna of northern South America direct 

 us to Africa." He believes (we shall discuss this later) that the 



Hill {Bull. Mus. Harvard, Vol. 34, 1899) says that at the end of the Cretaceous 

 and the beginning of the Eocene there was an extensive continental period, bi$t 

 that there was a subsidence at the end of the Eocene and in the Oligocene, and 

 then again an uplift at the end of the Oligocene and in the Miocene. The latter 

 is ju<-t the opposite movement from what is known for Cuba. It is quite likely 

 that a different fate is to be assumed for the different islands, and it seems that 

 Spencer's idea of contemporaneous subsidence or elevation of the whole region 

 between North and South America is entirely wrong; the orogenetic movements 

 and the changes of level connected with them were, after the first great subsi- 

 dence of the Caribbean basin, more or less local and affected only limited parts, 

 so that at the same time we may have had opposite movements in different sec- 

 tions of this region. 



