334 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. V. 



Pliocene formations appears to prevail generally in Cuba, in the South 

 Eastern States, and in the Windward Islands, while beds of that 

 period occur on the Tehuantepec Isthmus in Mexico. The degradation 

 was of long duration for the streams reduced their valleys to base levels 

 of erosion far inland on the continent, and their courses were marked 

 by broad valleys. On some of the lands which now form islands, the 

 same is true, for where not entirely removed the limestones often remain 

 only in fragmentary outcrops. 



The preservation of the older base levels of erosion, imprinted upon 

 the limestones, shows that the tablelands were not relatively as high as 

 at present, but the question of the late unequal terrestrial movements 

 becomes important in determining the Pliocene area of what are now 

 the islands. 



That the time of the elevation commenced somewhat earlier in one 

 locality than in another distantly located, and also ended in the same 

 manner, is probable. Where we find overlying accumulations resting 

 on the limestones, there we can judge of the relative duration and 

 character of the first period of denudation succeeding the early Miocene 

 deposits ; but at higher altitudes in Jamaica the period of degradation 

 has continued since the first elevation after the formation of the 

 limestones, consequently the erosion features represent the combined 

 characteristics of successive epochs of denudation. 



THE MIO-PLIOCENE HISTORY. 



EpocJi of Elevation. — The Mio-Pliocene period in Jamaica was charac- 

 terized by the elevation and dislocation of the " White Limestones " 

 and the subsequent long period of atmospheric degradation of the 

 existing land surfaces followed by a comparatively short one of the 

 formation of new beds of marine accumulations. 



The denudation of the old Miocene land surfaces which covered five- 

 eighths of the' island, represents the erosion in progress, more or less 

 continuously, since the first elevation of the Miocene strata, whether 

 before or after the middle of the Miocene period. Dr. W. H. Dall 

 informs the writer that he has seen no collection of Miocene fossils 

 from the West Indies which represent beds newer than the lower part 

 of the series (or the Oligocene). In making correlations between the 

 physical features and the fossiliferous strata, whose time divisions are 

 based upon the percentage of living forms only (and without such a 

 break as that on the northern continent, where the older Miocene beds 

 are characterized by a tropical fauna, while the later assemblage of 



