CANAL ZONE AND COLOMBIA 639 



certain localities are not mentioned, either because of the absence of fossil 

 plants or for the reason that no definite opinion seemed permissible. The 

 principal localities that are referred to are shown on the accompanying 

 sketch map (figure 1) and will be discussed in regular order. 



Canal Zone 



The described section in the Canal Zone (locality number 1) is of the 

 greatest importance in this connection, for while it is not a part of the 

 Andean system, the Canal Zone, because of its nearness to South America 

 and the rather definite correlation of its Tertiary formations, offers a 

 convenient standard for comparison. Moreover, the geological history 

 of the Isthmian region has a direct bearing on the facies of the marine 

 faunas of the west coast and the history of the terrestrial floras that have 

 entered South America from North America during those times that the 

 Isthmus was above the sea. The section need not be quoted in the present 

 connection, since the formations have recently been described by Mac- 

 Donald,^ and their correlation with the Tertiaries of our Southern States, 

 the Antilles, and Europe has been given in an important paper by 

 Vaughan.^ 



The geological history of the Isthmus arrived at by Vaughan indicates 

 that the region was emerged, and that there was no interoceanic connec- 

 tion across it during the whole of the Cretaceous and the earlier half of 

 the Eocene, and that there was free communication between the two 

 oceans during the Upper Eocene, Oligocene, and Lower Miocene. This 

 has an important bearing on the history of the floras and faunas of the 

 region to the southward, as I have already mentioned, and it will develop 

 on subsequent pages that this history corresponds with the history of the 

 opposite end of South America, and also accounts for the Mediterranean 

 elements found in the Tertiary marine faunas of Peru and Chile. 



Colombia 



Fossil plants have been described from two localities in Colombia. 

 These are Santa Ana (locality number 2), along the western margin of 

 the Eio Magdalen a Valley, and near Buga (locality number 3), in the 

 Rio Cauca Valley. The first is between the eastern and central and the 

 second between the central and western Andean chains. At both locali- 



2 D. F. MacDonald : U. S. Buioau of Mines, Bull. 80, 1015 ; IT. S. Natl. Mus. Bull. 103 

 (in press). 

 "T. W. Vaughan: TJ. S. Natl. Mus. Bull. 103 (in press). 



