204 
This is not the first instance of the finding of Orbiloides in the 
Philippines, for in 1901, Mr. Martin,* the recognized authority on the 
little-known paleontology of these Islands, published a short statement 
concerning Orbitoides which were found by Semper in a marl from 
Alpaco, Cebu. 
The importance of Orbitoides in the Philippine and Malayan stratig- 
raphy can not be brought out too strongly, for it is a typical zone 
fossil—i. e., widely distributed, but restricted in vertical range—and 
from it we have been able to make some interesting and highly important 
correlations which will be mentioned in the following pages. 
FIELD RELATIONS. 
Binangonan is situated on the western side of the western of the two 
peninsulas which extend southward into Laguna de Bay, due east from 
Cavite. It is reached by launch from Manila by way of the Pasig River. 
The surface rock throughout the country immediately north of Laguna 
de Bay is voleanic and consists of very recent trachytic and basaltic 
flows, while farther to the north and south is a vast tuff area, familiar 
to geologists from the literature of Abella, Von Drasche, Semper, Becker, 
and others. As one goes northeast along the old trail to the limestone, 
the ground rises rather gradually, until the backbone of the peninsula 
is reached, at an elevation of about 350 feet, from which altitude the 
surface drops away in a series of poorly preserved terraces to a broad, 
flat-bottomed valley on the east. 
That this valley was at one time an arm of the Laguna and also of the 
sea there seems to be little question, for on the highest bench just below 
the limestone cliff (fig. 1) two shells belonging to the genus C'rassatellites 
(marine) were found. 
Binaogones Ceveh of Laguna de Boy 
s 
Fic. 1.—Ideal section of part of Binangonan Peninsula. 
Almost identical species are living in Philippine waters to-day. 
On the western slope of the peninsula also, the evidence of recent 
uplift is indicated by the deep U-formed stream gorges. 
THE VOLCANIC ROCK, 
At Binangonan the lava is a dense, bluish-black, clean-cut basalt very 
much like some phases of the rock from Talim, but a little to the north- 
ward in the old city (Manila) quarry, whence the rock was taken for road 
metal, it becomes lighter colored and more cellular. A section of this 
has been examined with the petrographic microscope and found to be 
‘K. Martin: “Orbitoides von den Philippinen.” Centralblatt fiir U. @. P. 
(1901), 326, 327. 
