The Pre- Cretaceous of California. — Falrhanlx. 77 
shell, undoubtedly of this epoch, in the rocks of Alcatraz island, 
gave the additional desirable assurance of the correctness of our 
views."* In another place he sa^'s of this fossil: '-Presented to 
the survey by major George H. Elliot, U. S. Engineers, by whom 
the first specimens were discovered. On subsequently visiting 
this locality I found numerous casts of this and of several other 
bivalves, the latter in too imperfect a condition to be recognized. 
The species is of unusual interest, being the first incontestable 
proof of the Cretaceous age of the long disputed San Francisco 
sandstone."! A close examination of the island has recently 
been made, but no traces of any molluscan remains have been 
found. The sandstone of the island is identical with that of the 
mainland both north and south which I hold to be pre-Cretaceous, 
The genus Inoceramus is not confined to the Cretaceous. J. S. 
Diller has recently found specimens of it in the Jurassic of Plumas 
county, + while in the Cretaceous of California I believe it is con- 
fined to the upper division, the Chico, not being known in the 
Shasta group. The specimen found on Alcatraz island was not in 
good condition, and 1 think it can safely be said that there is room 
for doubt concerning the correct determination of this fossil. 
The other fossil which has been made use of to determine the 
Cretaceous age of the Coast ranges is a supposed vVucella from 
the Santa Lucia range, a little east of San Luis Obispo. It was 
found by Mr. Turner while gathering material for the report on 
the quicksilver deposits of the Pacific coast § In ' 'Correlation 
Papers," Cretaceous, Dr. White speaks of the most southerly 
known locality of the Aucella as near parallel 37 -degrees 30 
minutes north latitude, || that is, in the Mariposa beds, thus ig- 
noring the specimen from San Luis Obispo, which may have 
been determined wrongly. As European authorities in particu- 
lar disagree as to the time range of the genus Aucella, whether 
it is characteristic of the Jurassic or Cretaceous, or of both, it 
does not seem to be the proper thing to classify a great series of 
rocks by it alone. There has existed much uncertainty with re- 
gard to the exact classificatien of the Aucella in California, and 
*Geol. of Cal., Vol. i, p. 77. 
tPalivontology of Cal., Vol. ii. 
iBulI. Geological See. of America, \ol. in, p. 405. 
§(Teology of the (Quicksilver Deposits, p. 381. 
IIEuU. U. S. (Teological Survey. No. 82. 
