Bulletin of the Museum of Comparative Zoology 

 AT HARVARD COLLEGE. 



Vol. XXVIII. No. 5. 



(Geological Semes, Vol. III.) 



THE GEOLOGICAL HISTORY OF THE ISTHMUS OF 

 PANAMA AND PORTIONS OF COSTA RICA. 



BASED UPON A RECONNOISSANCE MADE FOR ALEXANDER AGASSIZ. 



By Robert T. Hill. 



WITH SPECIAL DETERMINATIONS BY 



William H. Dall, R. M. Bagg, T. W. Vacghan, J. E. Wolff, H. W. Turner, 

 and Ahe Sjogren. 



With Nineteen Plates. 



CAMBRIDGE, MASS., U.S.A.: 



PRINTED FOR THE MUSEUM. 



June, 1898. 



