284 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



EXPLANATION OF THE PLATES. 



PLATE I. 

 Map of the Isthmian Region. 



PLATE II. 

 Map of the Caribbean Region. 



PLATE in. 

 Map of Panama Bay. 



PLATE IV. 



Fig. 1. Topographic Profile across Costa Rica, natural scale. 



Fig. 2. Natural Profile of Isthmian Region. 



Fig. 3. Geologic Section across Isthmus of Panama, exaggerated vertical. 



PLATE V. 



Fig. 1. Amplified Details of Central Section. 



Fig. 2. General Section and Profile across Costa Rica, exaggerated vertical. 



PLATE VI. 



Fig. 1. Continental Section, Isthmus of Panama, showing Relation of Land Sur- 

 face to Submarine Platform. 



Fig. 2. Costa Rican Section showing Amplification of the Caribbean Side, Protru- 

 sions of Igneous Rocks through the Tertiarics and Base Level Plain. 



Fig. 3. Section of the Caribbean Slope, Province of Talamanca, by W. M. Gabb. 



PLATE VII. 

 Sjogren Section of Caribbean Slope of Costa Rica. 



PLATE VIII. 

 Typical Scenery, Isthmus of Panama. 



