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, 



Fig ore 4. Section at Vamos a 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 

 a Vamos beds is passed. Here the rocks still have a distinct dip to the 

 northward tow T ard the Caribbean. 



Kilometer 13£. — Another low mass of the Vamos a 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 10^-. — 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 a" 



