NORTH PACIFIC LAND BRIDGE 
329 
early Tertiary marine faunas, to those of California would 
thus receive a satisfactory explanation without invoking a 
land connection across Bering Strait. As soon as the marine 
channel which separated the coast hills in California from the 
rest of the country disappeared, a number of Asiatic immi¬ 
grants entered North America. But the flora, especially of the 
small islands lying off the coast of California, still bears the 
impress, as Mr. Greene* has pointed out, of belonging phyto- 
geographically to another continent than America. 
I also mentioned that the European invasion of North 
America, which travelled by the trans-Atlantic land bridge, 
had ultimately entered the Continent from the south-west. 
The two elements, the Asiatic and the European, must have 
joined there eventually. To judge from purely faunistic testi¬ 
mony, that was evidently the course of events (compare 
p. 211). Somewhere about the Miocene Period extensive sub¬ 
sidence of the land west of California must have compelled 
the fauna and flora to seek refuge on the continent with which 
the Pacific belt of land seems to have become united. Palaeon¬ 
tological evidence gives us reason for such a supposition. Take 
for example the great land-tortoises. Their sudden appearance 
in south-western Miocene deposits suggests that they came 
from the west with other new-comers. This hypothesis like¬ 
wise throws light on their survival near at hand in the Gala¬ 
pagos islands, which no doubt once formed part of the Pacific 
belt of land alluded to. There are such a variety of problems 
connected with this theory that I shall defer the further dis¬ 
cussion of it till the next chapter. In conclusion, a few addi¬ 
tional remarks on the nature of the supposed extension of land 
west of Central America will facilitate the comprehension of 
the scheme of land connections that have only been roughly 
outlined so far. 
When I described the remarkable fauna and flora of the 
Cape region of Lower California (p. 207) and their marked 
affinities to those of the opposite coast of Mexico, I made no 
reference to the fact that this interesting assemblage of 
animals and plants is living in a hilly district being separated 
from the nearest mountains to the north of it by a wide extent 
* Greene, E. L., “ Botany of Santa Cruz Island,” pp. 377—388. 
