THE MARINE TERTIARY OF THE WEST COAST 599 
closely related to the John Day (Upper Oligocene) form than to 
that found in the lower Rosebud (Lower Miocene) of the Great 
Basin region. While Dr. Stock has indicated the relationships of 
of the Tecuja vertebrate fauna to that of the John Day, he has 
also stated that it may occupy a position in the Tertiary transi- 
tional between Oligocene and Miocene. It seems to the writer 
that the stratigraphic and paleontologic evidence favors the 
Lower Miocene age of these beds rather than the Upper Oligocene. 
The most important evidence in favor of this last conclusion is 
that the invertebrate fauna of the Vaqueros as already stated, is 
very closely related to that of the Temblor, a very large percentage 
of the species being common to the two faunas. Some of the forms 
listed are types of considerable ornamentation and complexity and 
are known to have a fairly short geological range. On the other 
hand, the known fauna of the Vaqueros is very different from the 
known fauna of the San Lorenzo, and there is here a much greater 
faunal break than between the Vaqueros and the Temblor. In the 
section at the south end of the San Joaquin Valley, where the 
Tecuja beds occur, the Vaqueros rests directly and unconformably 
upon the San Lorenzo. . 
Climate.—The conditions of temperature during the Vaqueros 
and Temblor epoch seem to have been between warm-temperate 
and subtropical. The generic assemblages of the two horizons are 
very similar. The large lyropectens and dosinias are found in 
both, and a fairly high percentage of the species are common to 
the two horizons. This close relationship of the faunas indicates 
a similar temperature of the waters. 
One of the puzzling problems in connection with the origin of 
the Temblor deposits is the great thickness of organic shales that 
is found all along the coast of California and especially in the 
southern part of the state. In some localities these organic shales, 
a very large proportion of which are composed of the frustules of 
marine diatoms, have a thickness exceeding 5,000 feet. Diatomace- 
ous oozes in any considerable quantity are now only found in 
Arctic and Antarctic waters, and from this we might judge that these 
shales were deposited in cold water. However, the fossil molluscan 
faunas found in these shales, or closely associated with them, 
