this narrow b 
154 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The Orogenic Revolution of Later Tertiary 
Epeirogenic Movements of Post-Miocene Time 
Résumé of the History of the Tropical American Mainland 
Obscurity of the Paleozoic Record. . . . . . . . 
Possibility of Land Connection in Jurassic and Cretaceous š 
Possible Absence of Jurassic Marine Sediments on the ‘Atlantic 
side of the North and South American Continents . Ek 
Discordance of the Cretaceous Faunæ of the Atlantic and Pacific 
РІОУШСӨЕ;. s ea ears sd atu RI CSR A 
Early Assertions of Community of Atlantic and Pacific Fossil 
Forms based upon Insufficient Data . 
Results of Recent Researches. . . . . . Tu vols . 
Pacific Types in the Gatun Beds in Harmony with the Biologic 
Deductions that the Passage existed in the Eocene Tertiary 
Evidence not conclusive that the Isthmus of Panama was the exact Locus 
OPTS AE ER, e an E den VC лақтан АДЫ 
Absence of Known Tertiary Formations on the Pacific Side of Trop- 
багаар s МАМАМ deet e E e a UY s 
Lack of Testimony showing that the Eocene Passage was other than 
Shallow and ОКО a р, з, nor un а e үз v 1 
Absence of Off-shore Sediments indicating Deep-water Conditions . 
Harmony of Geologic and Biologic Testimony showing the Establishment 
of the Present Land Barrier at the Close of ће Miocene . . . . 
Both Biologic and Geologic Testimony oppose the Presumption of Marine 
Connection in Pleistocene or Later Time . ...... + * > 
Fallacious Data upon which Pleistocene Connection has been assumed . 
Summary and Conclusion Lb ЕСУІ, mh 
Part VI.— APPENDICES . . + 
Report by William H. Dall on the Tertiary Fossils 
Report by R. M. Bagg on the Tertiary Foraminifera. 
List of Corals identified by Mr. T. Wayland Vaughan . 
Report by J. Elliott Wolff on the Igneous Rocks . ЕУ 
Notes by Ahe Sjogren on the Eastern Section of Costa Rica . 
INTRODUCTION. 
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281 
Тнв problem of an interoceanic passage, which has attracted com- 
mercial exploration to the Isthmus of P 
discovery, is accompanied by no greater 
anama since the date of its 
fascination than that which 
has attended the purely scientific question of the geologio origin of 
continents. 
ond of union between the North and South American 
'The geological history of the Isthmus has been a subject of specula- 
tion. Zodlogists and paleontologists hav 
from the opposing shores, 
astute conclusions. 
e written upon the forms of life 
and by comparison have made many able and 
The Polyps, Echinoderms, Mollusks, Crustacean 
