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 the 
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 been 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 in 
regard to the recent marine fauna. 
A further complication, as Professor Gregory f pointed 
out, remains to be considered. It is not at all certain, lie 
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 havo 
been a gulf of the Pacific, separated from the Atlantic by the 
land area of the hypothetical “ Antiilia.” 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 P. Toula, “ Fauna von Tehuantepec,” p. 220. 
t Gregory, J. W., Palaeontology of the West Indies,” p. 305. 
L.A. R 
