42 BULLETIN : 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 Black water 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 the west of 

 Miami River, I found to my great surprise that it consisted entirely of 

 well stratified seolian rocks (Plate XIX.) the base of which had been 

 changed into base rock. This base rock could be traced on both sides 

 of the seolian bluff. On the east it extended to the mouth of the 

 Miami Biver, and beyond, on both sides of the river, the exposures on 

 the shores resembled the Bahama a?olian rocks, being honeycombed, 

 pitted, and full of pot-holes, and readily mistaken for reef rock. But I 

 saw no corals in any of the exposures examined. Professor L. Agassiz 

 found corals farther inland. The shore rocks on the southern edge of 

 the mainland, where I examined them, are certainly not reef rock ; they 

 are of seolian origin, and the elevated reef on the rear of which these 

 reolian 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 

 extremitj' of Florida alternate with reolian rocks, and how far inland 

 the latter extend, and what part of the Everglades they cover. 



Both L. Agassiz 1 and Shaler 2 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 ci-ops out at 

 Elliott Key, and west as far as Indian Key. The bottom of Key Bis- 

 cayne 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 arc 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 sea water which bathes the southern shores of 

 the main line of keys. In 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 rcolian rocks (Plate 

 XX.). In the p leading from Key Piscayne Bay past Cape Florida 



Lighthouse the bottom is hard, the current sweeping through with 



1 Mem. Mus. romp. Zool., Vol. VII. No. 1. 



2 Bull. Mus. Comp. Zool., Vol. XVI. No. 7. 



