18 FLORIDA REEFS. 
in width. Nowliere does it rise more than thirteen feet above the level of 
the sea. The hill ninety feet high, said to exist on its eastern extremity, 
resolves itself into a tuft of very high mangroves. 
The vegetation of the whole key is very rich, the trees more diversified 
and larger than on any other island in the range. The rock formations are 
also very diversified. The seaward shore is rather abrupt, the ocean hav- 
ing worn away the sloping edges. The foundation of the key consists 
chiefly of large coral boulders, the flat Ma^andrina heads being most numer- 
ous, though Porites and Astrteans are also abundant. They are so dis- 
tributed upon the lower level of the island that one would think they had 
grown where they are found. On closer examination they are seen to be 
detached coral heads heaped together, and, owing to their peculiar form, 
stranded in an upright position. Whoever has seen Ma^andrina heads broken 
off by boring shells will not wonder to see these flat hemispheres resting on 
their broad, flat bases rather than on their rounded side. But though they 
are thus found in their natural position, suggesting the idea that they have 
grown where they now lie, the fact that among them are some which are 
overturned, and others broken in halves, contradicts this conclusion, and 
show that, notwithstanding the regularity of the foundation, this key, like 
the others, rests on an accumulation of detached coral boulders. Indian 
Key has a similar foundation ; the evenness of the accumulation and the 
natural position of the heads misled me at first into the belief that I had 
found a proof of the upheaval of the keys. But a closer survey satisfied me 
that their upper formations consist here, as elsewhere, of coarse and fine 
oolites, with intervening seams, as at Key West, of compact limestone, and 
an overlying crust whereon the sea does not encroach upon the older 
formations. 
As has already been remarked, the shore is rocky, and, except in' small 
patches, no sand beach is seen along this extensive island. Thei-e are, how- 
ever, large mud flats along its southeastern extremity, among which rise 
Key Rodriguez, Dove Island, two Mangrove Keys, and another off Plantation 
Island, known as Tavernier Key. These mud flats abound in animals of all 
kinds. Nowhere are Holothuria more numerous ; cartloads might easily be 
gathered. The Eunices are also more numerous than elsewhere, and 
nothing can exceed the beauty of the Actinias, Gorgonias, and Chitons to be 
found on every rock upon the shore. The best evidence that Key Largo, 
notwithstanding the fictitious height assigned to some parts of it, may 
