Le Conte on the Coaht Islands of California. 77 
with it, but now separated by subsidence of the continental 
margin. They may be regarded as the highest points of an old 
coast range outside of the present coast range, the broad valley 
between the two being now covered with water. Moreover, 
the date of the separation may be determined with certainty. 
That they were connected with the mainland during the later 
Pliocene and early Quaternary is proved by the fact that re- 
mains of the mammoth have been found on Santa Rosa, the 
largest and one of the farthest off of them.^ They were^ there- 
fore^ undozibtedly separated durhig the ^ziateniary period. 
The main points in Mr. Greene's paper with which we are 
here concerned are the following: 
1. Out of 296 species of plants collected by him on the island 
of Santa Cruz, no less than 48 are entirely peculiar to these 
islands, and 28 peculiar to Santa Cruz itself. 
2. Of the remaining 248 species nearly all are distinctively 
California II- — that is, species peculiar to California are very 
abundant, while common American s'pecies, i. <?., those common 
to California and other parts of North America, are very few 
and rare. The flora as a whole, therefore, may be regarded as 
distinctively Californian, with the addition of a large number of 
species wholly peculiar to the islands. 
3. A number of rare species found in isolated patches, and? 
as it were, struggling for existence, in the southern counties — 
San Diego and San Bernardino — are found \n great abundance 
and very thriving condition on the islands. 
4. Lavatera., a remarkable malvaceous genus of which 18 
species are known in the Mediterranean region, and one from 
Australia, but not a single species on the American continent^ 
is represented on these islands by four species. This is certainly 
a most remarkable and significant fact. 
Such are the facts. I account for them as follows: 
California, especially the region west of the Sierra Nevada, 
is geologically very recent. The Sierra region was reclaimed 
from the sea at the beginning of the Cretaceous, and the coast 
region as late as the beginning of the Pliocene. When first 
emerged the coast region was of course colonized from adjacent 
1 Proc. Cal. Acad, of Sci., vol. v., 152. 
