50 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



sion are known to every skipper who anchors off its shores. Green 

 Cay has been extended by this sand bore to the very edge of the plane 

 where the sudden drop in depth beyond the 20 fothom line takes place. 

 The seolian rocks of Green Cay crop out at the eastern edge of this sand 

 bore. Against these outcrops the bore rests, and in some places has com- 

 pletely overwhelmed them. At the eastern extremity of the western 

 spit a mass of blocks of teolian rock has been piled \ip by some hurri- 

 cane. On Green Cay we find the same pup<T3 so characteristic of all the 

 Bahamas. The vegetation reminds us of that found on Eleuthera along 

 the shore line. The principal mass of Green Cay, which rises to a height 

 of sixty feet, is of seolian origin ; but the extent of the cay is greatly 

 modified by its being a buttress for the sand bores which extend from it 

 both to the westward and eastward. Green Cay is marked among the 

 Bahamas for the combination it presents of sand bores and seolian rocks, 

 and shows how some pai'ts of the banks themselves may have been 

 formed of movable bores at certain stages of their subsidence, when 

 masses of sand large enough to become afl'ected in their movements by 

 the action of the sea and of the winds had accumulated from the dis- 

 integration of fixed nuclei of teolian rocks. It is very easy to imagine 

 such a process as we saw going on at Green Cay to liave been an impor- 

 tant fiictor in connecting adjoining hills or in filling low valleys between 

 neighboring islets. Green Cay is the only cay left to indicate the former 

 existence of the land which once extended round the edge of the Tongue 

 of the Ocean all the way from New Providence to the islets to the south 

 of Andres, parallel with the line of the 100 fathom soundings, which 

 now alone indicate its probable original outline. 



Andros and the Western Part of Great Bahama Bank. 



Plate XI. Figs. 1, 3; Plate XII. Fig. 3; Plate XXXIII. 



From Anguila Island we crossed the Santaren Channel during the 

 night and made for Wide Opening early in the morning. When in sight 

 of Andros we made a haul for a specimen of the bottom, and obtained our 

 first sample of the so called " white marl," wliich is marked on the charts 

 as extending many miles west of tlie Wide Opening of Andros, as well as 

 to the north and south, forming a liuge triangular patch characterized 

 by this peculiar bottom. It consists of a very fine chalky ooze, resem- 

 bling plaster of Paris which has just been mixed for setting. 



From our anchorajre to the shore of Andros at the mouth of Wide 



