1905. | AMPHIBIANS AND REPTILES. 235 
and Guatemala, also the Mexican Sierra Madre del Sur. These 
parts were in time annexed by Sonoraland. 
By the late Hocene, conditions were so far consolidated that 
there existed the present North American Continent, eastern and 
LAND DURING 
EAREY CRETACEOUS EPOCH. 
It 
Diagrams to illustrate the contours of Mexico at different geological ages. 
western halves joined, and the latter extending southwards as the 
present Mexico and part of Central America. Brazilia had grown 
into South America, but the two continents were still separated, 
the Atlantic and Pacific communicating across the present 
Isthmus of Panama and probably further north. 
