20, 2 Dickerson: Review of Philippine Paleontology 197 
those of Pennsylvania and were deposited in deeper marine 
waters and not in the quiet waters of a low-lying coastal plain 
that characterized the conditions of deposition of the coal for- 
mations of Pennsylvania. This definite conclusion was reached 
only by a careful comparison of the fossil floras and faunas from 
the two states. 
Paleontology is not merely of negative value, but is of great 
positive use in guiding exploration and in recognizing geological 
structures suitable for drilling. A small collection of fossils is 
obtained from a new locality and among them are certain horizon 
markers which are always associated with coal. At once the field 
is explored for this valuable fuel. In this way, the exploring oil 
or coal geologist is able to pick out likely areas, and he need not 
spend time in hopeless regions of volcanic rocks or barren sedi- 
mentary beds. 
In oil-well drilling many times the bits bring up very small 
but determinative fossils, and sometimes the only evidence of 
the underlying structure is obtained in this way. Near Topila, 
Mexico, in the Anderson well, many small fossils were -collected 
in this maner from a depth of 1,800 feet (550 meters). From 
a study of this fauna the writer concluded that the rocks 
containing this assemblage were upper Eocene in age and were 
essentially equivalent to beds outcropping in the United States 
Gulf region many kilometers distant but not exposed on the 
surface in that part of Mexico. This discovery indicated the 
probable depth of possible production in this territory and was 
economically important on this account. 
Again, in a wild-cat well near Waldorf, California, the bit 
brought up several small fossil snails, all of the same species, 
from a depth of 2,000 feet (610 meters). These small snails, not 
over 1 centimeter long, proved to be Bittiwm camulosensis, a 
characteristic fossil of the San Fernando Pliocene. Now, the 
oil in this region generally occurs below this formation, well 
down in the Vaqueros of Middle Miocene age. The locators 
thought they started in the Miocene at the surface, but this 
indisputable evidence indicated that they were mistaken in this 
regard ahd either that they had still from 900 to 1,200 meters to 
£0 (an impossible depth for economic production) or that a great 
fault occurred near this well site! The well was abandoned. 
As will be shown later in this paper, the fossil clams and 
Snails occurring in the Tertiary enable us to correlate some of 
these beds with the oil-bearing horizons of Java and Sumatra. 
This correlation clearly indicates broadly that there are pos- 
Sibilities of economic production of petroleum in the Philip- 
