THE FLORIDA REEFS. 69 
All this evidence tends to show that the coral reefs had little, 
if anything, to do with the building up of the peninsula of 
Florida north of Cape Florida. The existing line of veef is in- 
deed probably the only one which has played any important part 
in the formation of land south of the line of the present south- 
ern extremity of the peninsula of Florida. There seems, how- 
ever, some reason to believe that a line of reefs, or perhaps two 
lines not very distant from each other, once stretched along the 
southeastern end of the Everglades before the present reef began 
to extend westward. Judging from the sections shown by the 
maps, the growth of the present reef, as fast as the mud flats 
were formed to the south of it, has been altogether in that di- 
rection. (Figs. 40, 41.) 
The Bahamas, the San Pedro, and Yucatan banks have pro- 
bably all been formed by a similar process, — by the accumula- 
tion of limestone either upon an early fold of the earth’s crust, 
or upon a voleanic plateau, or upon a foundation of slower 
growth from great depths. In Yucatan we can actually descend 
into the bank itself through any one of the aguadas, or caverns, 
found everywhere in the northern part of that country. Many 
of these caverns extend to a considerable depth; one of them, 
that of Bolonchen, has a depth of seventy fathoms, the whole 
formation consisting of recent limestone entirely composed of 
species of invertebrates now living on the Yucatan Bank. In 
Yucatan, as in Florida, we find a low ridge of limestone, some- 
what older than that of the coast, extending across the peninsula. 
The uplifting of this ridge has caused the slight undulations of 
the surface traceable throughout Yucatan, at a distance of from 
twenty to thirty miles from the coast, and running nearly at 
right angles to it. Judging from its fossils and lithological 
characters, the limestone of which this ridge is formed is iden- 
tical with the so-called Vicksburg limestone of the central 
backbone of Florida. The fauna of the Yucatan Bank is iden- 
tical with that of the Florida Bank, being characterized by the 
same species of echinoderms, mollusks, crustaceans, corals, and 
fishes, so well known already from shallow water on the Florida 
side. 
While on the Yucatan Bank I had the opportunity of exam- 
