Vol. VII] DICKERSON— ANCIENT PANAMA CANALS 203 



States that in no place in the entire region has a commingling 

 of upper Cretaceous faunas of these two provinces been found. 



According to Hill,'"' during Cretaceous time the major 

 islands of the Antilles were started on the crests of oceanic 

 volcanoes. These land masses thus built up were submerged 

 in part and the sediments deposited from their erosion con- 

 tain a fauna of upper Cretaceous age. At the end of Cretaceous 

 time these strata were folded along northwest-southeast axes. 

 In late Eocene and early Oligocene time a profound regional 

 subsidence occurred during which all but the highest tips of the 

 Antilles were covered by the waters of the Caribbean. This 

 subsidence was followed by an uplift in Oligocene time, during 

 which great orogenic movements along east-west axes took 

 place. This was the stage, if at all, of an Antillean continent. 

 Possibly many of the larger islands were connected at this 

 time, and the southern portion of Florida may have been linked 

 with this large Antillean island. This event was succeeded by 

 another great submergence and portions of Mexico and Central 

 America as well as the major portions of the Antilles were 

 largely covered with oceanic waters, the Bowden stage. 



According to the work of Scott^" and Matthew^^ in the study 

 of recent and fossil mammals, any connection of the mainland 

 with the Antilles is very improbable. The species of small 

 sloth found in the Pleistocene beds of Cuba sprang from a 

 single form which evidently reached this locality via one of 

 the raft routes. It appears quite probable that other mammals 

 in Cuba and other islands migrated in this way. 



Scott shows that during Miocene time the mammalian faunas 

 of North and South America were entirely distinct. These 

 facts indicate that a period of widespread submergence oc- 

 curred during the Miocene and the beds bearing the Bowdeu 

 fauna may well represent this era of subsidence. 



DalP"* has compared the Bowden fauna to that of Bordeaux 

 and the Aquitanian. Guppy^" has also compared the fauna 

 to the Dax Miocene and the Bordeaux. The age of the Aqui- 

 tanian has not yet been definitely settled. De Lapparent"* 



'^Hill. R. T., Bull. Mus. Comp. Zool., vol. 34, 223, 1899. 



"Scott, W. S., History of Land Mammals of the Western Hemisphere, 1913. 



"Matthew, W. D., Climate and Evolution. Annal. N. Y. Acad. Sci., p. 204 1915 



" Dall, W. H., Proc. U. S. Nat. Mus., vol. 19. 1897. 



>» Guppy. K. J. L., Geol. Mag. Sept.. 1874. 



» De Lapparent, Text Book of Geology, 1912. 



