38 bulletin: museum of comparative zoology. - 



thrown up by the sea, all the way from that point to Soldier Key, 

 which is the last exposure of the southern face of the patches visible on 

 the hue of the keys. AVhile their northern face, traced by Professor 

 Shaler on the mainland back of Cocoanut Grove to a height of nearly 

 twenty feet, is separated from it by the whole width of Key Biscayne 

 Bay, which has washed away all traces of the connecting reefs and of 

 the smaller sinks separating its patches and bars. 



The most prominent points at which the elevated reef crops out are 

 Sand Key, Bahia Honda, Indian Key, Key Largo, Lower Matecumbe, 

 Old Rhodes, Elliott, Bagged, and Soldier Keys. That the elevated reef 

 must have been greatly eroded Shaler has already shown in his section 

 from Key Biscayne Bay, extending into the Everglade district. From 

 what has been observed by Professors Agassiz, Shaler, and myself on 

 the southern edge of the mainland, there are now found there great 

 patches of ajolian rocks filling intermediate sinks and alternating with 

 patches of reef rock of greater or less extent, or perhaps covering the 

 connecting coral ledge. 



The well preserved condition of the elevated reef of the Florida Keys, 

 as well as that of the northern shore of Cuba, would seem to be a strong 

 argument in favor of the view taken by Shaler, that the elevation, or 

 the series of elevations, which took place in Florida in the present geo- 

 logical period, must have been more or less paroxysmal iu their nature. 



Shaler adopts the view of the formation of the peninsula of Florida, 

 as well as of the Bahama Bank, as due to a great fold, formed per- 

 haps by the growth or accumulation of material upon the floor of the 

 Gulf of Mexico, and he looks upon the formation of the Yucatan and 

 Mosquito peninsulas as the counterpart of that fold on the southern 

 face of the Gulf of Mexico. . "We should remember, however, that the 

 Greater Antilles, as well as the Windward Islands, can scarcely be 

 looked upon as part of the same counter thrust. They are of volcanic 

 origin, and have an independent history of their own. Shaler certainly 

 overestimates the amount of material now derived from Cuba, which 

 finds its way to the Straits of Florida. At one time that must have 

 been very considerable, as is well shown by the enormous denuda- 

 tion of its limestone mountains, but at the present day it is of little 

 importance. 1 



A glance at the charts of the extreme southern part of Florida 



1 Roe A. Agassiz, "A 'Reconnois-:m< v of the Bahamas," Bull. Mns. Comp. Zool., 

 Vol. XXV. No. 1, p. 1<>^: also, R T. Hill, " Notes on the Geology of Cuba," Bull. 

 Mus. Conq.. Zool., Vol. XVI. No. 16, p. 267. 



