AGE OF CENTRAL AMERICA 241 



The species in question are, in the first instance, two sharks, 

 viz., Carcharhinus nicaraguensis and Pristis antiquorum, as 

 well as Pomadasis grandis and others whose ancestors are 

 marine forms. The antiquity of the region is indicated by 

 the occurrence both in Lake Nicaragua and Lake Managua 

 of the Central American gar-pike (Lepidosteus tropicus). 



The studies of geographical distribution, particularly those 

 of marine species, have thus led to the conclusion that tha 

 Central American land bridge has been in existence certainly 

 since pre-Glacial times. No zoologist has suggested even the 

 possibility of a submergence of Central America having taken 

 place as late as the Pleistocene Period. No biological support 

 can be given, therefore, to the theory which has beien advanced 

 by some writers, that the Glacial Period was due to a diversion 

 of the Gulf Stream across the isthmus of Panama. On the 

 other hand, Central America was certainly submerged by a 

 shallow sea in two or more places in early Pliocene or Miocene 

 times. Another very important character, which is revealed 

 both from a study of the recent and fossil marine fauna, is the 

 Atlantic facies of the animals. The movement of the species 

 seems to have taken place from the West Indian area towards 

 the Pacific Ocean, thus implying the existence of a strong 

 current in that direction. Speaking of the Tertiary deposits 

 of Tehuantepec, Dr. Bose * remarks that the main mass of the 

 species contained therein are related to Atlantic forms. Only 

 very few show affinities with Pacific types. Similar views 

 were expressed by Professor Jordan and Dr. Ortmann an 

 regard to the recent marine fauna. 



A further complication, as Professor Gregory, f pointed 

 out, oremains to be considered. It is not at all certain, he 

 thinks, that when the Isthmus of Panama was submerged 

 there was free communication between the Atlantic and the 

 Pacific Oceans. The Caribbean Sea, he argues, may then have 

 been a gulf of the Pacific, separated from the Atlantic by the 

 land area of the hypothetical " Antillia." As I shall show in 

 the next chapter, which deals with the origin of the West 

 Indian fauna, the Caribbean Sea could not have been' .separated 

 from the Atlantic Ocean at so late a geological period as that 



* Bose, E., and F. Toula, " Fauna von Tehuantepec," p. 220. 

 t Gregory, J. W., Palaeontology of the West Indies," p. 305. 

 L.A. B 



