48 bulletin: museum of comparative zoology. 



for many miles southward and northward of Exuma Harbor, and forms 

 one of the prettiest stretches in the Bahamas, there are many diminutive 

 cays, isolated rocks of all sizes, with rounded ridges undermined at the 

 water's edge and ready to topple over and disappear. The seolian rock, 

 kept constantly wet, becomes soft and readily crumbles, and is washed into 

 ajolian rock sand. The whole floor of the harbor is covered with fine 

 sand of this kind, and the harbor is gradually filling with material de- 

 rived from the wash of the windward row of outer islands. Off Exuma, 

 between it and the northern end of Long Island, the edge of the bank 

 is comparatively wide. The British Admiralty Chart, No. 393, shows 

 admirably the gradual wasting of the land which has taken place to form 

 the inner sound. ^ There was comparatively little animal or vegetable 

 life on the floor of the harbor where we examined it. On leaving Ex- 

 uma we sounded at short intervals, and found the sea slope of the bank 

 much less steep and more gradual than that of other faces we had 

 explored. 



From Conch Cut to Green Cay. 



Plate XXXVI. 



From Exuma Harbor we steamed northward to Conch Cut, keeping as 

 close as was prudent to the outer line of cays, which all showed indica- 

 tions of great erosion. On the northern extremity of Groat Exuma the 

 ajolian hills are closely packed, and reach a height of one hundred and 

 fifty feet. The islands of Lee Stocking and Great Guana present the 

 usual features of seolian hills attacked by the sea at the base of the longer 

 slope. The smaller cays are bare, while even on Exuma and the larger 

 cays the vegetation is far less luxuriant than we might expect from the 

 size of the islands. 



Passing through Conch Cut to enter upon the bank on our way to 

 Green Cay, we were struck with the number of small islets, which 

 form a wide protecting belt against the encroachments of the sea. The 

 islets are all exposed on the lesser slope of the ajolian hills to the action 

 of the trade swells, while the steeper face has been attacked by the 

 shorter, sharper waves reaching across the bank, and undermining the 

 western faces of the islets to an extraordinary degree. The solvent action 

 of the sea water has also undoubtedly played an important part in pro- 

 ducing the fantastic shapes which some of the islets and isolated rocks 

 have assumed ; so that by this combined action a wide shallow bank 



1 See also U. S. Hydrographical Charts, Nos. 26'> and 26". 



