THE BAHAMA ISLANDS 15 



vegetation which has become adapted to this semi-arid environment. The 

 leaves of these shrubs support large numbers of land-shells, which feed on them 

 and at death become detached and falling to the ground accumulate about the 

 base of the plants. Drifting sand quickly covers them over and they become 

 true fossils. In digging around the roots of these plants, one can uncover a 

 large number of these shells. As the dune thickens and grows in height, these 

 organisms become buried deeper and deeper and, when the sand solidifies to 

 hard rock, they become cemented into one mass with the surrounding particles. 

 Vegetable remains and especially casts of roots occur abundantly in the 

 geolian deposits. These are particularly noticeable where the waves have etched 

 out the softer parts of the matrix and have left the more consolidated casts 

 to stand out in relief, giving to the surface a rough and scoriaceous appearance 

 (Plate III, Fig. 2). 



AQUEOUS DEPOSITS. 



The deposits formed by the agency of water have either been laid down 

 at the bottom of the small ponds described above or by the waves and currents 

 of the ocean. The deposits made at the bottom of the small lakes are of 

 little extent. They, however, are of considerable importance in that they 

 carry the remains of the organisms which inhabit the various brackish water 

 lakes. Great Lake in the interior of Watlings carries large numbers of shells ; 

 also the salt pans on Rum Cay (Plate XC, Fig. 1). The deposits which line 

 the bottoms of these salt pans contain large numbers of fossil shells, which 

 belong to a fauna derived from the ocean outside but adapted to living in their 

 peculiar environment. The fossils collected at Eum Cay were submitted to 

 Dr. Dall who has discussed them in another chapter. 



In many places it was found that these aeolian deposits rested on lower 

 beds of marine origin, which were frequently very fossiliferous. Localities 

 where these marine beds were observed finally became so numerous and were 

 so widely distributed that the conviction became irresistible that the substratum 

 of the Bahamas, throughout at least the northwestern portion of the archipelago, 

 was marine. At certain places, as for instance, on Rum Cay, these marine 

 deposits extend as high as 15 or 20 feet above sea level. The asolian deposits 

 are therefore to be considered as a superficial blanket covering these basal 

 marine sediments. A list of localities where these marine deposits were found, 

 together with the fossils from each, is given by Dr. Dall in the next chapter. 



A quarter of a mile west of Clarence Harbor the contact between the 



