EXPLORATIONS IN CAPE REGION. 755 



At the end of the glacial period the sierra of the Cape 

 Region probably consisted of a low island, with morains 

 ten to fifteen miles long, sloping down to the sea. These 

 morains did not cross the narrow valley of San Jose, nor 

 did I find any remains of such morains east of this valley, 

 though I may remark that my explorations in this region 

 have been very imperfect. 



RELATIONS AND ORIGIN OF THE FAUNA. 



From our geological and other observations, it is evi- 

 dent that at the end of the great ice period the Cape 

 Region of Baja California existed as an isolated island, 

 separated by a broad sound, perhaps several hundred 

 miles wide, from the main part of the peninsula, while 

 from the main land of Mexico there probably existed 

 the same distance as at present. This island must have 

 had little or no animal life, there being an entire absence 

 of lowlands on which a milder climate would have made 

 it possible for animal life to subsist and retain itself, while 

 the higher mountains were wrapped in snow and ice. 

 This rocky island must have been several thousand feet 

 high, with no bare ground exposed to the warmth of the 

 sun. As the ice melted away and the soil was exposed, 

 the land gradually rose, bringing with it a lowland sur- 

 rounding the mountains. The first immigrants of animal 

 life must have been temperate forms, which again, as the 

 climate became warmer, ascended to the mountains, while 

 the later and more tropical forms remained in the lower 

 lands. 



To begin with, only such animals could have immigrated 

 to the Cape Region as were able by some means or other 

 to cross the ocean from the mainland. But as later on 

 the Cape Region became connected with the peninsula 

 by a low stretch of land, immigration of animals became 

 much easier and permitted an inroad of northern species 



