FLORIDA REEFS. 23 
selves. Living in communities, death begins first at the base or centre 
of the group, while the surface or tips still continue to grow, so that it 
resembles a dying centennial tree, rotten at the heart, but still apparently 
green and flourishing without, till the first heavy gale of wind snaps the 
hollow trunk and betrays its decay. Again, innumerable boring animals 
establish themselves in the lifeless stem, piercing holes in all directions into 
its interior, like so many augers, dissolving its solid connection with the 
ground, and even penetrating far into the living portion of these compact 
communities. The number of these boring animals is quite incredible, and 
they belong to different families of the animal kingdom : among the most 
active and powerful we would mention the date-fish, Lithodomus, several 
Saxicava, Petricola, Area, and many worms, of which the Serpula is the 
largest and most destructive, inasmuch as it extends constantly through the 
living part of the coral stems, especially in Mfeandrina. 
On the loose basis of a Ma?andrina, measuring less than two feet in 
diameter, we have counted not less than fifty holes of the date-fish, — some 
laro-e enough to admit a finger, — besides hundreds of small holes made 
by worms. 
But however efficient these boring animals may be in preparing the 
coral stems for decay, there is yet another agent, perhaps still more 
destructive. We allude to the minute boring-sponges, which penetrate 
them in all directions, until they appear at last completely rotten 
throughout. 
The outer reef, or, as it is generally called on the spot, The Reef, is the 
main seat of the present activity and growth of the reef-building corals in 
Florida. This reef consists of a narrow wall, rising nearly to the surface of 
the water, with a steep seaward slope, and a gentler one on the inner side 
toward the ship-channel. Its greatest width varies from one to two miles, 
though it is frequently not more than half a mile wide. This is true, for 
instance, of all those narrow ledges which have risen to within a few feet of 
the surface, such as Fowey Rocks oft' Soldier Key, Triumph Reef off 
Ragged Key, Long Reef off Elliott's Key, Ajax Reef off Caesar's Creek, 
Pacific Reef off Old Rhodes, Turtle Reef off the eastern extremity of Key 
Largo, and the extensive reef of Carysfort facing for several miles Key 
Largo. This spot is one of the most instructive on the reef Here the reef, 
for a stretch of several miles, nearly reaches the surface and forms a long 
level ledge entirely covered with living corals (chiefly the large spreading 
