GEOLOGICAL HISTORY OF FLORIDA 
171 
the end of the Miocene Period, while a slight depression 
occurred in Pliocene times, and little change since. Whether 
the tropical flora of southern Florida, or part of it at any rate, 
is the relict of an Oligocene invasion from the south is left 
undetermined by Dr. Dali’s researches. Yet, from the fact 
that a species of the terrestrial mollusk Glandina occurs in 
the Pliocene Caloosahatchie beds of south-western Florida, 
we might be led to infer that other southern forms might 
have survived on the peninsula till Pliocene and possibly 
recent times. 
Dr. Hill concurs in so far with Dr. Dali’s conclusions 
as he establishes in Jamaica signs of a tremendous orogenic 
movement in late Oligocene or Miocene times, resulting in an 
uplift whereby many of the West Indian Islands and pos¬ 
sibly an insular southern portion of Florida became united 
with one another. In Miocene or early Pliocene the islands, 
according to Dr. Hill,* were severed from one another by 
submergence, assuming gradually their present outlines which 
they have since retained. 
That some kind of union of the island of Florida with the 
West Indies took place in Miocene times is likewise indicated 
by Dr. Matthew f in his attempt to delineate the hypothetical 
outlines of the continents in Tertiary times, for he distinctly 
unites southern Florida and Cuba by land. 
According to Dr. Vaughan,ij: the Florida plateau already 
existed in pre-Oligocene times, but it was only towards the 
end of the Oligocene Period that a portion of the plateau rose 
above the sea and apparently remained so ever since. 
Although this constituted only a small island (“Orange 
island ” as he calls it), the deposits of the whole plateau are 
full of sand and arenaceous material implying proximity of 
land. 
From the opinions cited on the geological history of Florida 
it is evident that there is nothing distinctly antagonistic to 
the view that part of the tropical flora of southern Florida 
is a relict from Tertiary times, many of the species being 
* Hill, Robert T., “Geology of Jamaica,” p. 224. 
t Matthew, W. D., “ Continents in Tertiary Times,” p. 366. 
f Vaughan, T. W., “ Geologic History of Floridian Plateau.” 
