200 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



excellence, by failing to correlate the threefold testimony of config- 

 uration, biology, and geology have been led into serious errors of 

 deduction. 



Vague indeed is knowledge of the history of tropical regions prior to 

 the Cretaceous period. Eocks of an earlier epoch are but sparsely and 

 imperfectly exposed, being concealed even where they probably occur by 

 the overlay of later sediments and volcanic ejecta. We know that the 

 Appalachian and allied regions of the United States, as far west as the 

 98th meridian, since Paleozoic time, have been great bulwarks of land, 

 against the southern front of which the northern waters of the Gulf of 

 Mexico extended in Cretaceous and Eocene time, and that these old 

 lands prior to their degradation and burial in late Mesozoic time occu- 

 pied much of the southern and eastern Coastal Plain. There are also 

 areas of old Mesozoic land of smaller dimensions in the Cordilleran 

 regions of northwestern Mexico and the southwestern United States. 

 In southern Mexico, Guatemala, and possibly Cuba and Haiti, there are 

 long east and west ridges of Paleozoic rock, which may have had some 

 fundamental relation to the east and west trends so largely dominating 

 in the tropical region, or possibly foreshadowing the present outlines of 

 the Great Antilles. In northern Venezuela another stret-ch of Paleozoic 

 or Archaean rocks is reported to extend from the Andes north of east 

 to the Caribbean coast and through the island of Trinidad. Paleozoic 

 rocks also probably occur beneath the volcanic debris of Central America 

 in Nicaragua, Honduras, and Costa Rica. The oldest rocks of Cuba and 

 Haiti have been doubtfully considered of Paleozoic origin. Such are the 

 earliest foundations of the great tropical amphitheatre in which during 

 Mesozoic and Cenozoic times conflicts between laud and ocean have con- 

 tinued, and from which amidst the vicissitudes of migrating shore lines, 

 great oscillations of level, and volcanic extrusions, the present configura- 

 tion of land surfaces and ocean bottoms have been evolved. In all of 

 these localities south of the United States the events of Paleozoic and 

 older Mesozoic history have been obliterated by the overwhelming phe- 

 nomena of Cretaceous and later time, — buried beneath the oceanic sedi- 

 ments or volcanic ejecta, so that the interpretable history of the region 

 may be said to begin with Cretaceous time. 



There is some evidence that during the long period between the Ap- 

 palachian revolution, after the close of the Carboniferous and the begin- 

 ning of the Lower Cretaceous (Wealden epoch), the Atlantic borders of 

 the North American coast met the Atlantic Ocean far eastward of the 

 present continental outline, and that this expansion of the land was at 



