MUSEUM OF COMPARATIVE ZOOLOGY. 281 
that time. At any rate, if there had been any long epochs of subsi- 
dence, they would be recorded in great fiord-like valleys or low passages 
across the central axis of the island, such as do not exist, and to which 
the oval harbors may not be compared, for the origin of these is due 
entirely to the pre-existing fringe reefs. 
It might be alleged that all the ancient topography showing subsi- 
dence is still beneath the ocean level, and that the angular edges of 
Cuba are indicative of the fact that the present outline merely represents 
an ancient summit which is re-emerging. The submarine topography, 
however, is not within the province of this paper, but I agree with Pro- 
fessor Agassiz that its irregularities were indicated long before the period 
of history herein recorded. The three alternations of gravel and reef in 
the Matanzas section may also have indicated slight alternations of sub- 
sidence and elevation. 
Without committing myself to an emphatic negation as yet, I must 
confess that no evidences of great subsidence are apparent at present, 
and although I hold my conclusions upon this subject in abeyance to 
future observations, I seriously doubt its existence. 
It is now possible, with the aid of the stratigraphic and paleontologic 
data previously given, to make afew conclusions concerning the Ceno- 
zoic history of Cuba. It has been shown by the stratigraphy that the 
topographic levels are not old reef levels, but that, with the excep- 
tion of the modern reef, they have all been carved out of the old 
Tertiary limestones, which had previously been folded and disturbed by 
movements that could not have been generally uniform, but which were 
orogenic, and hence the present bench topography of Cuba is subsequent 
to this period of Post-Tertiary wrinkling, and represents a different kind 
of movement, which was regional or epeirogenic. Since the old folding 
or orogenic movement occupied at least a small portion of Post-Tertiary 
time, we may reasonably conclude that the two great periods of uniform 
uplifting recorded in the old levels must have taken place at least. since 
the beginning of the Pleistocene. In other words, they are compara- 
tively modern in geologic time, — some of them absolutely recent. 
It is not maintained in this paper that these epochs of regional 
elevation were continuous and uninterrupted, or unaccompanied by 
pauses or even alternating epochs of subsidence, but that their general 
progress has been periodically upward, and that, if there were epochs of 
subsidence they are difficult to distinguish, and were of short duration, 
and insignificant in comparison with the great uplifting movement that 
has generally taken place. 
