No. 5. — The Geological History of the Isthmus of Panama and 
Portions of Costa Rica. Based upon a Reconnoissance made 
for ALEXANDER Agassiz. Ву ROBERT Т. HILL. 
TABLE OF CONTENTS. 
INTRODUCTION . 
Parr I. — Tue GrooraPatc "POSITION | OF THE  ISTHMIAN REGION 
Independence of the North, Central, and South American Orogenic Sys- 
tems 
Тһе Later Volsanio Mountains, - ‘their Distribution ‘and Relation to the 
Folded Regions 
Physical Differences between the Lands surrounding the Caribbean Sea 
and the Gulf of Mexico 
'The Greater Isthmian Region includes the whole of Central America 
The Recent Volcanic Eminences mostly on the Pacific Side 
The Caribbean Side a Region of East and West Mountain Folds . 
The Isthmus of Panama defined UR 
'The Mountainous Topography of the Isthmus S 
Absence of a Dividing Continental Ridge 
Тһе Coastal Topography void of a well defined Coastal Plain 
The Drainage of the Isthmus 
The Isthmian Topography contrasted with that of the adjacent Andean 
and Costa Rican Heights . UP s 
"Topographie Evidence of the Antiquity of the Isthmus . 
Parr IL — Tur GEOLOGY or THE CONTINENTAL SECTION, Conor TO 
PANAMA . 
'The Caribbean Coast 
Colon Harbor 
Manzanilla Island. 
Manzanilla Bay 
The Isthmian Swamps . 
Colon to Bujio d 
The Monkey Hill Base Level 
The Inland Swamps . 
The Foraminiferal Marls ot Bujto . ` 
Section from Bujio to Colon along the Line of the Panama Canal ү 
Bujio to the Pacific CRT 
The Barbacoas Subsection 
The Bujio Formation 
The Pena Negra Hill 
VOL. XXVIII, — NO. 5. 1 
