340 HANNIBAL: A PLIOCENE FLORA FROM CALIFORNIA 
these some recent species may be expected and a comparison can 
then be made. However, the important changes in climate and 
humidity, which took place in the continental history of California 
at the opening of the Pliocene’ have gone a long way toward 
eliminating these types. With their extinction appeared full- 
fledged and apparently unheralded, the modern California flora. 
It is obvious that the several peculiar genera and numerous species 
which characterize it could not have come into existence and 
become fixed types in the brief interval, geologically speaking, 
between the upper Miocene and late Pliocene. It is reasonable 
to assume that this flora, already developed to its present high 
specialization, immigrated from elsewhere, where, through a very 
considerable period of time, it had evolved. 
The Santa Clara flora cannot be compared with other floras 
of corresponding age, since no other Pliocene floras have been 
described from North America.” Such floras occur in England™® 
and other parts of Europe, but consist entirely of local species. 
Quaternary plants are known in the Loess of Canada" and the 
marine deposits of Maryland” but are likewise too remote to 
afford comparison. 
formation, Upper Miocene, associated with Astropadsis Whitneyi and other char- 
acteristic marine mollusca. No magnolias or chestnuts are now indigenous to 
California, and but few of the other species have any living relations west of the 
Rocky Mountains. 
16 While the nena relations of the Contra Costa and Kettleman Lake 
beds are known with considerable certainty, of the entire faunas, totaling some 
species se psa i mollusks, only two, Anodonta cygnea impura and 
Paludestrina Pgtirage are common to the two formatio These occur again in 
the Santa a beds and still exist, widespread, from es Oregon east to the 
ocky ret ean and south well into Mexico. The other Contra Costa species 
suggest strongly the fauna living in the lower Mississippi Valley. The Kettleman 
fauna on the other hand is the precursor of the existing central California fauna. 
It seems probable that the abrupt change of conditions which eliminated the 
Miocene flora was coincident with that which eliminated the Miocene fresh-water 
mollusca. The latter took place during the comparatively brief interval separating 
the Contra igs and Keaeunen periods of sedimentation, and it is presumed the 
former did a 
gina F. H., Jour. Geol. 18: 1910, has reported Woodwardia sp.» 
Sassafras sp., and Sterculia sp. from the ai of the Columbia River, in beds sai 
to be of Pliocene a 
8 Reid, C., & = M. Jour. Linn. Soc. 38: 206. 1908. 
1 Dawson and Penhallow. Bull. Geol. Soc. Am. 3: 311. 18 
2 Hollick, A. Pliocene and Pleistocene. Md. Geol. Sur. sak: 148, 217. 
