NORTH PACIFIC MARINE FAUNA 
95 
while 61 per cent, at present occur exclusively north of 
this locality. Professor Arnold* is thus led to the con¬ 
clusion that semi-tropical conditions prevailed during the 
deposition of the Pleistocene formation. He also emphasises 
the fact that the later Tertiary and Pleistocene faunas of 
Japan and the west coast of the United States resembled one 
another much more than the faunas of the two sides of the 
Pacific do at the present time. 
Nothing could be more contradictory than the two state¬ 
ments of Dr. Dali and Professor Arnold as to the climatic 
conditions prevailing in 'two portions of the Pacific coast of 
North America in Pliocene and Pleistocene times. It seems 
almost as if the deposits from which Dr. Dali derived his con¬ 
clusions were not contemporaneous with those that led Pro¬ 
fessor Arnold to pronounce the views just stated. It is 
scarcely possible to conceive that, while a warm-water fauna 
existed on the Oregon and Alaskan coasts in Pliocene times, 
California should have had a cold climate. Arctic conditions 
are then supposed to have supervened on the north Pacific 
coast. On the Californian coast, on the other hand, the cold 
Pliocene climate is stated to have been succeeded by a semi- 
tropical one during the Pleistocene Period. 
It is now generally recognised, I think, that Central 
America, in its present configuration, originated by a final 
union of pre-existing independent land-masses in Pliocene 
times. That an inter-oceanic current, now no longer exist¬ 
ing, might have produced altogether peculiar climatic con¬ 
ditions on the Californian coast in Miocene times but 
not later seems admissible. If we suppose that the Japanese 
“ Kuroshiwo ” current formerly sent part of its warm 
waters through a wider opening at Bering Strait into the 
Arctic Ocean, would it have had the effect of inducing 
the Mexican fauna to advance northward and the arctic 
fauna to pour southward towards the coast of Oregon ? 
I doubt, even under such geographical conditions, whether 
the Pleistocene faunas of California and Oregon could 
have differed to such an extent as described by Dr. Dali and 
* Arnold, Ralph, “ Marine Pliocene and Pleistocene of San Pedro,” 
pp. 65—67. 
