STRUCTURE OF THE TURKS ISLANDS 273 



explanation of " things Bahamian," which, although based mainly on 

 zoological evidence, makes a serious claim on some of the geological 

 testimony that the " anti-extensionist " is wont to regard as peculiarly 

 his own. 



The remarkable similarity in geological structure between the 

 Bermudas and the Bahamas is rightly emphasised by Scharff in his 

 Distribution and Origin of Life in America (1911, p. 185) ; and he is 

 justified in doing so, since the peculiar geolian formation of these two 

 regions cannot be matched on the same scale in any insular region of 

 the globe. Should the same formation exist in Florida, the point 

 would acquire yet more importance. Laying stress on the zoological 

 argument that we are not concerned here with land- areas stocked 

 with " waifs and strays," but with ancient land-surfaces possessing 

 faunas often peculiar in their character, he advocates the hypothesis 

 that in Tertiary times the Bahamas and the Bermudas were included 

 in a land- area that joined together the Greater Antilles and was 

 connected with Florida (p. 186, and maps facing pp. 280, 294). 



He points out (pp. 288-9) that although displaying affinities with 

 neighbouring regions, the Bahamas possess reptilian, amphibian and 

 molluscan faunas that are often largely their own. In this connection 

 Dr. Scharff could have also summoned to his aid the witness of the 

 plants. In the tropical Pacific, low islands, like those of the Bahamas, 

 would have been stocked through the agencies of birds and currents 

 with cosmopolitan and wide-ranging plants, and would have dis- 

 played little or no endemic element. On the other hand, the plants 

 of the Bahamas, as shown in Chapter XII., exhibit a marked Bahamian 

 impress ; and present characters that could only have been developed 

 during ages of isolation from other regions. 



Note added August 2, 1916. — It will be shown in one of the last 

 notes of the Appendix that according to Dr. Vaughan and other 

 American geologists the similarity in geological structure between 

 the Bermudas and the Bahamas extends to the seolian origin and 

 calcareous character of the deposits, but not to their mechanical 

 condition. A reply will there be made to the query concerning the 

 occurrence of this formation in Florida. 



Summary 



1. The low islands of the Turks Group, which belong geographic- 

 ally and botanically to the Bahamas, possess the geological features 

 so characteristic of that archipelago. They are composed in their 

 higher parts of seolian sandstone, which is made of consolidated 

 calcareous drift-sand, and in their lower parts of coral-reef debris 

 thrown up under the existing conditions of sea-level. They possess 

 all the other general characters of the Bahamian Islands, which are 

 situated on banks that at the eastern extremity of the archipelago 

 rise from the ocean's depths and at the western end have shallower 

 connections with the North American continent and the island of 

 Cuba. 



2. It is pointed out that only in coral-reef regions could we look 

 for the conditions that have produced a great archipelago with such 



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