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ranges as a whole, but will be suggestive of what may be true 
of all. 
The age of the Santa Cruz Mountains can with little question be 
placed at the end of the Merced period. Unfortunately, we are 
not as yet able to say exactly what is the age of the topmost 
beds of the Merced series. The highest beds from which fossils 
were obtained gave a small fauna, all of whose forms are living 
on the coast today, thus seeming to be of Pleistocene age. 
Including the fossiliferous beds which occur a few feet further 
down, and which must be included with the top beds, the fossil 
fauna shows 81 per cent. of living forms, thus seeming to be of Plio- 
cene age. The most that can be said is that the post-Merced uplift 
occurred just about the end of the Pliocene or early in the Pleisto- 
cene. In either case these Coast Ranges of California are among 
the youngest mountain ranges of any prominence in the world. 
Turning to the San Fernando Range, we find the topmost 
beds concerned in the uplift and folding of the range correspond 
with the lower or transitional beds of the Merced period, thus 
placing their age about the end of the Miocene or beginning of 
the Pliocene. 
Further confirmation of this is found in a study of the hori- 
zontal fossiliferous deposits along the coast, as at Santa Barbara, 
San Pedro, San Diego, etc. Thus, at San Pedro in Los Angeles 
county, there is found first the shales of the Monterey series 
dipping south. Above them unconformably come first a little 
sand dune or wind deposit, then a few feet of quite fossiliferous 
sand, then a top fossiliferous layer. 
The top layer is unquestionably Pleistocene. A study was 
made of the fossiliferous layer just below. Altogether 125-150 
species were collected in this layer, of which number 104 species 
have been determined. Of the 104 species identified 99 or 95 
per cent. are known living. But many of those living are only 
known now in, for example, the Arctic fauna. Thus it is found 
that of the 104 species twenty-six have not been reported from 
the coast near San Pedro, leaving seventy-eight species of 104 
fossil species known to be living, or 75 per cent. 
