180 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
it largely to be. On closer examination, however, this is found to be 
of undoubted sedimentary character, being distinctly stratified, and ac- 
companied by great round black calcareous concretions, full of fossil 
shells. The exposure (Fig. 4) has, in general, a strong dip of over 30 
degrees toward the Caribbean coast. These rocks are intensely faulted, 
FrGunE 4. Section at Vamos á Vamos. 
jointed, and in some places slightly folded. This is one of the most in- 
teresting and important localities of the whole Central American region, 
and will be frequently referred to in this report. The fossils collected 
from this locality have been examined by Dr. Dall, who definitely refers 
the age of the deposit to that of the Claiborne epoch of the Eocene 
Tertiary. 
Surrounding the base of this bluff on both sides of the river the banks 
are mostly alluvial clay, and contain lignite in small pieces. It is evi- 
dent that most of the region has long since been base-levelled with the 
exception of this hill, so that it now stands as the remnant of the limb of 
a former anticline. 
Kilometer 20 to Kilometer 15. — I was unable to form any conclusion 
concerning the red clay formations of the banks along this portion of the 
course. They may be old river alluvium, which has been spread over 
an eroded surface, or the less indurated residuum of the Tertiary beds. 
At Kilometer 15. — Another outcrop of the water's edge of the Vamos 
4 Vamos beds is passed. Неге the rocks still have a distinct dip to the 
northward toward the Caribbean. 
Kilometer 134. — Another low mass of the Vamos 4 Vamos formation 
appears on both sides of the canal, covered by the red clay. 
Kilometer 12. — Black and blue-black lignitic alluvial clays continue 
to form the banks. 
Kilometer 104.— The Mindi Hill Beds. — Here a deviation of the 
canal turns off into the river towards Gatun, and the marls in the banks 
of the river begin to change in character and appearance, The older 
Vamos beds are succeeded by green sand marls of a finer, more uniform 
and homogeneous texture and structure, void of lamination. They are 
evidently a higher subdivision of the same Tertiaries as the Vamos á 
