158 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 
the outcrops of these fossil reefs at the southern extremity of the Everglades 
are only outlyers of the southern extension of these northern rocks. To the 
damming up of the waters in the Everglades, and to the sudden outbursts of 
gigantic masses of water charged with organic matter and lime, we may trace 
the immense destruction of fishes which so frequently occurs on the shores of 
the Florida keys and the waters surrounding them. 
ALEXANDER AGASSIZ. 
