222 BULLETIN : MUSEUM OF COMPARATIVE ZOÖLOGY, 
On closer study this system presents several interesting minor trends, 
and its history reveals a complexity of movements. In Jamaica, for 
instance, and those islands around the Windward passage in the very 
heart of the region, two movements of different epochs and axial direc- 
tions can be traced. The oldest of these produced the intense folds of 
higher summits of eastern Cuba, Jamaica, and western Haiti, com- 
posed of terrigenous and volcanic débris of Eocene and Cretaceous 
age. A subsequent subsidence destroyed the pre-existing continuity, 
and coated the lower slopes of these mountains with 3,000 feet of 
purely oceanic deposits. This was followed by another uplift of Mid- 
Tertiary time, which was produced or accompanied by the vast igneous 
intrusions. The trends produced by these two events are quite distinct. 
Those of the older uplift are northwest and southeast in Jamaica and 
Haiti, and continued with the Sierra Maestra of Cuba, and constitute 
an almost closed amphiteatre of summits, broken only in the west by 
the Bartlett Deep. 
The trends of the later Miocene uplift, which added the present white 
limestone areas to the Antilles, are strictly east and west, and the struc- 
ture is that of simple open anticlinal folds, 
In the Panama and Honduras trends active vulcanism was in opera- 
tion during the earliest of these mountain making epochs, the chief 
erupted material being augite-porphyrites. The second orogenic epoch 
in the Antilles was accompanied in the Panamic, Costa Rican, and 
Carribischen ranges by intrusions of a different nature, 
The foregoing facts all lead to the conclusion that the orogenic” 
growth of the cross ranges of the Tropical region was a series of inter- 
mittent processes. These were probably initiated back or before the 
early Mesozoic, as shown by the uplifts of the Segovian ranges which 
are concentric with the southern margin of the older Appalachian 
trends. This may have been followed by movements in the later 
Mesozoic not yet deciphered. The chief revolutionary movement ef- 
fective in producing the present configuration occurred in the Miocene 
Tertiary. The Post-Eocene age of these uplifts is undoubtedly attested 
by the fact that in all the regions mentioned, including the Segovian, 
where older rocks also occur, the ranges are composed of intensely 
folded Eocene and Oligocene strata which have been cut through by 
granitoid and basic intrusives. 
Concerning the origin and succession of volcanic events, the follow- 
ing facts can be stated. In late Cretaceous time vulcanism was active 
