1877.] The Flora and Fauna of the Florida Keys. 139 
Thus in the past forty years, Looe Key, part of Sand Key, and 
North Key, at the Tortugas, have been swept off and replaced by 
shoals. 
The actual western termination of the system of keys is at 
Loggerhead Key, one of the Tortugas, but shoal ground ex- 
tends some twenty miles farther west. The reef proper termi- 
nates opposite the Marquesas, about forty miles east of the Tor- 
tugas. The ancient reef which preceded the one which formed 
the keys did not extend as far west by more than one hundred 
miles, terminating about Cape Sable.1 
The formation of the keys to the westward of Key West 
plainly shows their more recent origin. The Tortugas consist 
mostly of coarse coral sand, sometimes unconsolidated, sometimes, 
as at Loggerhead Key, forming a soft rock, quite different from 
the harder limestone of Key West. At Loggerhead its very 
recent origin is plainly seen by its containing occasionally pieces 
of metal from wrecks, such as bolts, nuts, nails, ete. East Key 
of the same group seems to be washing away at its southern end 
and forming anew at the north. North Key, which has been 
mentioned as having disappeared, is said to have had the only 
well of fresh water in the group. It was explained by my in- 
formant, probably correctly, as having been composed of very 
fine sand, more apt to retain the rain-water unmixed than the 
coarser sand of the other keys. 
The marine fauna of the coral region of South Florida is a 
West Indian colony engrafted on the more or less North Amer- 
ican fauna of the east and west coasts of the peninsula. From 
Cape Florida and from Cape Sable northward the reef corals and 
their commensals are not found, the calcareous is replaced by 
silicious sand, oyster banks fill the bays, and a great change is 
apparent by a mere look at the prevailing shells thrown up on the 
beaches. í ; 
The flora of the keys is very largely West Indian in its ori- 
gin. Mr. Frederick Brendel has given in yol. viii. No. 8, of this 
journal, interesting remarks on the species of plants common to 
fossil Corals found in them would be of interest to compare with more recent ones, 
Pith the coast. I take this opportunity to say that the Museum of Comparative 
93y in Cambridge would be thankful for a set of the fossil corals of Tampa Bay. 
