Contributions to tlie Fauna of tlie Bahamas 



9 



500 t'atlioDis deep, on the southwest by the narrow Old Bahama Channel from 

 Cuba, of about 200 — 300 fathoms in depth, and on the south by a rather narrow 

 but deep channel (2000 fathoms) from Haiti. (Map II.) Toward the Atlantic the 

 banks dip down suddenly to a depth of 2500 fathoms. On the north the banks 

 are much more developed than on the south, forming two large banks, on which 

 several of the principal islands are situated, the Little Baliama Bank with Bahama 

 Island and Abaco, and the Great Bahama Bank with Andros, New Providence, 

 Eleuthera, Cat Island, Exuma and Long Island, besides a great number of small 

 keys. These two banks are separated from each other by the Providence Channel, 

 which sends a branch (Tongue of the Ocean) to the south, giving the (ireat Bahama 

 Bank the shape of a V. As mentioned above the erosion has given rise to a great 

 number of small banks, on the south separated from each other by rather deep 

 channels, the general depth of which is 1500 fathoms. They are to a greater or 

 less extent occupied by islands, the principals being Watlings, Rum Cay, Crooked, 

 and Acklin Isl., Mariguana, Great and Little Inagua, Caicos and Turks Isl. 



A geological study of the Islands has shown tliat they are troughout built 

 up on the great bank — at present submerged and eroded — by coral sands and 

 minute fragments of shells and other calcareous organisms. When deposited by the 

 waves the sand has been heaped up to hills by the wind and in time got cemented 

 to limestone, thus forming hard rocks (Fig. A). The Islands are œolic. An exel- 

 lent view of the structure of the hills is given at Queen's Staircase in Nassau, the 

 capital of the islands, where the rocky hill is cut through (Fig. B). At many places 

 far inland from the beach corals are found in the rocks. Agassiz came to tlie 

 conclusion that they, together with marine shells also found there, were brought 

 there by the hurricanes, and had recemented in the rocks. That this is not always 

 the case, but that the islands are formed by corals also to some, though certainl}^ 

 only to a very slight extent, is clearly shown by the occurrence of a large coral 

 head above sea level on Green Cay, observed by the Expedition of the Geogr. Soc. 

 of Baltimore. During my visit to Andros I very often saw corals far from the beach 

 and on rather high places; and I think it would be to exaggerate the powers of 

 the hurricanes to consider them all to have been brought there in such a way. 

 From what is stated above it is evident that the Bahamas have an oceanic origin, 

 a fact which is of great importance for the study of the land fauna. There is a 

 special interest in this point. The Bahamas are not so isolated as oceanic islands 

 usually are, but as has been shown above are situated, together with all the West 

 Indian islands, on large banks, old mountain-chains, which were once elevated above 

 sea level, but at present are to greatest extent submerged. That the present Baha- 

 mas were formed at much later time than that at which these banks perhaps con- 

 nected North with South America and the West Indies with Central America, is 

 quite evident from a study of the geology of the Islands. But it is a priori not 

 impossible that after the formation of the islands an elevation could have taken 

 place, connecting some of them with neighbouring islands or with Florida or at 



Lunds Univ:s Årsskrift. N. F. Afd. 2. lid 7. 2 



