49 JULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
smaller sounds, on the west by two, and on the south by Largo Sound ; 
the land limiting these sounds being all parts of Largo Island, more or 
less connected, or separated by very narrow channels. It is easy to 
imagine such a sound as Blackwater Sound, with its fringe of land, 
becoming isolated and forming a cluster of islands very similar to that 
of the Marquesas. 
On examining a prominent low bluff about a mile to tho west of 
Miami River, I found to my great surprise that it consisted entirely of 
well stratified æolian rocks (Plate XIX.) the base of whieh had been 
changed into base rock. This base rock could be traced on both sides 
of the æolian bluff. On the east it extended to the mouth of the 
Miami River, and beyond, on both sides of the river, the exposures on 
the shores resembled the Bahama eolian rocks, being honeycombed, 
pitted, and full of pot-holes, and readily mistaken for reef rock. But I 
валу no corals in any of the exposures examined. Professor L. Agassiz 
found corals farther inland. Тһе shore rocks on the southern edge of 
the mainland, where I examined them, are certainly not reef rock ; they 
are of жоПап origin, and the elevated reef on the rear of which these 
seolian beds were blown has disappeared. It now remains to be seen 
how far the reefs, or the belt of patches of reefs, of the southern 
extremity of Florida alternate with eolian rocks, and how far inland 
the latter extend, and what part of the Everglades they cover. 
oth L. Agassiz" and Shaler? describe in detail the corals they have 
observed from one to three miles inland from the point I examined 
this time. Shaler describes the corals as a part of an elevated coral 
reef reaching a greater altitude than the reef which crops out at 
Elliott Key, and west as far as Indian Key. The bottom of Key Bis- 
onyne Bay near the northern extremity, about three miles from the 
entrance to the Miami River, is covered with Thalassia; the waters of 
the bay itself are of a dark brownish color, apparently saturated with 
vegetable matter. The dark color of the inland waters of the sounds 
back of the keys from Key Biscayne to Blackwater Sound is in marked 
contrast with the clear sca water which bathes the southern shores of 
the main line of keys. Іп some parts the bottom of the bay consists 
of fine dark gray sand, somewhat sticky. Near the shore Mr. Griswold 
has shown it to be covered with partly decomposed reolian rocks (Plate 
XX.). In the passage leading from Key Biscayne Bay past Cape Florida 
Lighthouse the bottom is hard, the current sweeping through with 
1 Mem. Mus. Comp. Zool,, Vol. УП. No. 1. 
2 Bull. Mus. Comp. Zoól., Vol. XVI. No. 7. 
