356 
ORIGIN OF LIFE IN AMERICA 
interchange would have continued only between Europe and 
South America. If the land bridge had then become discon¬ 
nected with South America, and joined to western North 
America, while the Antilles were submerged, the latest Euro¬ 
pean emigrants would have taken refuge in California as the 
last remnants of the old land sank into the Pacific. That 
something of this kind actually took place I feel convinced, 
although the details of these events must be founded largely 
on geological studies which unfortunately are as yet insuffi¬ 
ciently known. My own knowledge, moreover, of the geo¬ 
logical features of the regions alluded to is only fragmentary. 
Nevertheless, the little I have been able to gather does not 
tend to contradict the general scheme of the theories I now 
suggest. 
In later Cretaceous times a broad sea, as I have pointed 
out on several occasions, separated western from eastern North 
America, while the Pacific Ocean flooded a large portion 
of the western States, so as to leave only a comparatively 
narrow strip of land between the two seas. The Cretaceous 
deposits can be traced all along the Pacific coast as far almost 
as the extreme tip of Lower California. Here they suddenly 
stop. The Cretaceous sea evidently did not cover the in¬ 
teresting Cape Region of Lower California nor any part of 
western Mexico. There are reasons for the belief that even 
at this time the western part of the coast ranges of California 
were not submerged, thus suggesting the existence of another 
land-mass to the west of the Californian Sea. This land may 
have been connected with the Cape Region of Lower Cali¬ 
fornia, and thus with Mexico. By the end of Cretaceous time, 
says Professor Smith,* the subsidence and erosion of the 
western part of the continent had almost established a con¬ 
nection between the Pacific Gulfs in California and Oregon 
and the old Mediterranean Sea in the Mississippi valley. The 
intervening isthmus was covered by extensive marshes. Pro¬ 
fessor Smith tells us that the geographical conditions re¬ 
mained the same in Eocene times as in the Upper Cretaceous, 
except that the sea encroached still further on the land. Now 
it is precisely at this time that we notice a striking affinity 
* Smith, J. Perrin, “ Geological History of California,” pp. 347—348. 
