THE FLORIDA REEFS. 69 



All this evidence tends to show that the coral reefs had little, 

 if anything, to do with the building up of the peninsula of 

 Florida north of Cape Florida. The existing hne of reef is in- 

 deed probably the only one which has played any important part 

 in the formation of land south of the line of the present south- 

 ern extremity of the peninsula of Florida. There seems, how- 

 ever, some reason to beheve that a line of reefs, or perhaps two 

 lines not very distant from each other, once stretched along the 

 southeastern end of the Everglades before the present reef began 

 to extend westward. Judg-ino; from the secti' ns shown bv the 

 maps, the growth of the present reef, as fast, as the mud flats 

 were formed to the south of it, has been altogether in that di- 

 rection. (Figs. 40, 41.) 



The Bahamas, the San Pedro, and Yucatan banks have pro- 

 bably all been formed by a similar process, — by the accumula- 

 tion of limestone either upon an early fold of the earth's crust, 

 or upon a volcanic plateau, or upon a foundation of slower 

 growth from great depths. In Yucatan we can actually descend 

 into the bank itself through any one of the aguadas, or caverns, 

 found everywhere in the northern part of that country. Many 

 of these caverns extend to a considerable depth ; one of them, 

 that of Bolonchen, has a depth of seventy fathoms, the whole 

 formation consisting of recent limestone entirely composed of 

 species of invertebrates now hving on the Yucatan Bank. In 

 Yucatan, as in Florida, we find a low ridge of limestone, some- 

 what older than that of the coast, extending across the peninsula. 

 The uplifting of this ridge has caused the slight undulations of 

 the surface traceable throughout Yucatan, at a distance of from 

 twenty to thirty miles from the coast, and running nearly at 

 riofht anofles to it. Judoiuo: from its fossils and litholojrical 

 characters, the limestone of which this ridge is formed is iden- 

 tical with the so-called Vicksburg limestone of the central 

 backbone of Florida. The fauna of the Yucatan Bank is iden- 

 tical with that of the Florida Bank, being characterized by the 

 same species of echinoderms, moUusks, crustaceans, corals, and 

 fishes, so well known already from shallow water on the Florida 

 side. 



While on the Yucatan Bank I had the opportunity of exam- 



