21 6 CRUISE OF THE BARRERA 



the silt deposited by the rivers bringing down the 

 sands and mud from the high lomas and sierras 

 to the east. In late Tertiary times the western 

 end of Cuba as already suggested was marked 

 by Capes Avalos, Pinatillo, and Colorado, and the 

 then western coast followed thence roughly a line 

 passing not very far south of the present Mendoza. 

 The river depositions derived from the sierras and 

 lomas and poured into the shallow sea immediately 

 bordering the coast became but little admixed with 

 coral sand and reef detritus. The elevation of the 

 peninsula is along an axis coincident with the 

 south shore, giving to that coast line a more abrupt 

 appearance {farallones) . From the greater ele- 

 vation of the south shore, the land tilts downward 

 to the north, ending, as already noted, in a low- 

 lying swampy area along the north coast. Not 

 having had opportunity to study the farallones 

 of the south coast I can only hazard a guess that 

 the elevation of the peninsula was about two 

 hundred feet along its axis. The uplift of the 

 Guadiana sea bottom was much less. The differ- 

 ences in character and general aspect of these two 

 regions are well marked. The Guadiana basin is 

 a flat sandy prairie or savanna with occasional 



