FLORIDA REEFS. 17 
and one sinks ankle-deep in the dense coral growth. A most astonishing 
variety of sea-worms is found between the branches of the Pontes and 
Ociilina. This is also the play-ground of many Ophiurans and Asterians. 
Cidaris metularia are found here also, and other species of Echini. Such 
mud-shoals, composed of the most minute sand and mud, frequently encircle 
the keys, often extending for miles beyond their shores. Wherever they 
are laid bare at low water they are overgrown by Miileporas ; but where 
they are always covered, even at the lowest tides, with a few inches of water, 
the Porites take the ascendency. The latter are chiefly of two species, the 
Porites furcata and Porites clavaria. A black Ascidian is often attached to 
their branches in great numbers. Great numbers of Holothurians make their 
home upon these mud flats. Large holes, sometimes close together, some- 
times at small distances from each other, are frequently to be met with. 
These holes, widening at the surface in the shape of a funnel, having a depth 
of several feet and a diameter of several inches, are occupied by a gigantic 
worm of the genus Eunicea. Large Actinice of various colors are also numer- 
ous, and a deep orange colored Starfish and Manicinas show themselves 
also, though not in great numbers, and an endless variety of Gorgonias. 
Such shoals are the best field for the collector. Similar mud flats are found 
everywhere around the Mangrove Islands. But of these, more presently. 
Soldier Key rises about five miles to the south of Cape Florida. It is 
connected with an extensive mud flat, which stretches nearly to the lighthouse, 
being separated from it only by a narrow channel from nine to ten feet 
deep. The Ragged Keys come next, — a series of some half-dozen small 
islands formed by coral boulders rising but little above the surface of the 
water, and surrounded on both sides, and especially on their western shores, 
by wide mud flats. These keys, as well as Soldier Key, are covered by man- 
groves. It is noticeable that some of the Mangrove Islands have beaches, — 
a fact explained by their mode of formation. To the Avestward follows 
Elliott's Key, the first whose surface does not consist solely of coral boulders, 
coral sand having formed a succession of layers of oolitic rock upon it. Here 
also we first find white sand beaches dipping to seaward, and see a variety 
of trees mingling with the mangroves. On the southernmost extremity 
there is a spur formed by a mud flat, while another more extensive one 
juts to the eastward, and is connected with Old Rhodes, the next key. Key 
Largo, which follows, is the largest of all the islands in the main range of 
keys. It is not less than twenty-five miles long and from one to three miles 
