Geology of California. — lurner. 323 
that is, in the Mariposa beds, thus ignoring the specimen from 
San Luis Obispo, which ma}' have been determined wrongly. " 
The following letter on this point is self-explanator}' : 
"Washington, D. C, Feb. 8th, 1893. 
Dear Mr. Turner: 
In reply to your note calling my attention to the fact that I had 
not referred in my bulletin, No. 82, of the U. S. G-eol. Survey, to 
your discovery of Aucella at San Luis Obispo, I have onl}^ to sa}- 
that the omission was inadvertent. The specimen which you send 
me with yovw note, with the statement that it was found at that 
locality, is an Aucella of the type that I have referred to A. con- 
centrlca. Ym-y truly yours, 
C. A. White." 
It 3'et remains to be shown, however, whether or not the sandstones at 
Alcatraz island containing Iiwceramus and east o£ San Luis Obispo 
containing Aucella are of the same age as the phthanites and asso- 
ciated hardened sandstones and diabases. There is a large amount 
of red phthanite on the San Francisco peninsula where it is largeh' 
used in making roads. Whether the " San Francisco sandstone" 
is of the same age as the phthanite has not 3'et been proven in a 
satisfactoiy manner. My recollection is that there is no phthanite 
in the immediate vicinity of the sandstone near San Luis Obispo 
containing Aucella, and therefore this find cannot be taken as evi- 
dence of the age of the metamorphic series. 
The San Luis Obispo sandstone, however, resembles to a re- 
markable degree the tutfaceous sandstone, No. 75, from Knoxville, 
which would seem to indicate that it is later in age than the phtha- 
nite and diabase. 
The best evidence that has been l)rought forward up to the pres- 
ent time for considering that the Knoxville beds are unconform- 
ably deposited on the Coast range metamorphic series appears to 
be, first, the apparently sharp contacts of the two sets of rocks, and 
second, the occurrence of the debris of the metamorphic series in 
the Knoxville beds. 
Mr. Fairbanks treats of the rock of the Gavilan range and its 
continuation southward on page 71. He considers the granite of 
that range intrusive in the metamorphic rocks, and gives some observ- 
ations on the relation of the two series in a side gulch of Nelson 
creek. 
The rocks next to the granite, however, are described as being 
limestone and mica schist. Further up the slope occur phthanites, 
