280 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



logic evidence, for Dr. L. Stejneger says in his herpetology of Porto 

 Rico that "St. Thomas and St. John form only a herpetological ap- 

 pendix to Porto Rico," and Dr. P. Bartsch informs me that the 

 testimony of the land mollusca is the same as that of the reptiles 

 and batrachians. Indentations at depths of about 40 fathoms in the 

 outer edge of the submarine bank simulate hanging valleys that may 

 have been formed while the sea level was 40 fathoms lower than at 

 present. 



In the Virgin Islands there are three tiers of coral reefs, namely, 

 (1) on the outer edge of the deepest flat, (2) on the outer edge of the 

 intermediate flat, (3) within depths of 10 fathoms or less. The reefs 

 could not have been formed on the deepest flat while the scarp on 

 the landward side of the flat was being cut, and the other reefs are 

 clearly younger than the basements above which they rise, for their 

 basements existed and had had a complicated history prior to 

 the formation of the living reefs. In fact, the basements were dry- 

 land surfaces during at least a part of Pleistocene time. 



CUBA. 



The principal contributors to the literature on the shore-line phe- 

 nomena of Cuba are W. O. Crosby, 1 Alexander Agassiz, 2 R. T. Hill, 3 

 Vaughan and Spencer, 4 and Hayes, Vaughan, and Spencer. 5 I have 

 in papers cited on pages 271, 272 referred to some of the features of 

 the Cuban shore line as bearing on the conditions under which the liv- 

 ing coral reefs off the shores of the island have formed. W. M. Davis 

 has recently alluded to the origin of the pouch-shaped harbors, 6 and 

 here it may be well to direct attention to a criticism made by him 

 in his article cited in the foot note. He says: 



It is, however, worth noting that the embayments here considered have a quite 

 different relation to the adjacent coral reefs from that found, according to Hayes, 

 Vaughan, and Spencer, in the pouched-reef 7 harbors of Cuba; All the embayments 

 [ saw inside of sea-level barrier reefs in the Pacific islands occupy valleys older than 

 the reefs; but in Cuba the valleys, and still more the subsidence which drowned 

 them in producing the pouched harbors, are described by the above-named authors 

 as younger than the elevated reefs which inclose them; and such valleys do not bear 

 on the origin of the reefs, as appears from the following extract: * * * 



The extract is followed by comment, then by a quotation from 

 Crosby and one from Hill, after which he says : " Without additional 



i Crosby, W. O., On the elevated reefs of Cuba, Bost. Soc. Nat. Hist. Proc, vol. 22, pp. 124-130, 1883. 



2 Agassiz, A., A reconnaissance of the Bahamas and of the elevated reefs of Cuba in the steam yacht 

 Wild Buck, January to April, 1893, Mus. Comp. Zool. Bull., vol. 26, pp. 108-136, 1894. 



3 Hill, R. T., Notes on the geology of the island of Cuba, Mus. Comp. Zool. Bull., vol. 16, pp. 278-281, 

 1895. 



4 Vaughan, T. W., and Spencer, A. C, The geography of Cuba, Amer. Geog. Soc. Bull., vol. 34, pp. 105- 

 116, 1902. 



6 Hayes, C W., Vaughan, T. W., Spencer, A. C, Report on a geological reconnaissance of Cuba, pp. 

 123, 1902. 



« Davis, W. M., A Shaler Memorial study of coral reefs, Amer. Journ. Sci., ser. 4, vol. 4Q, pp. 227-228 

 1915. 



i "Pouched-reef harbors" are words not used in the publication under discussion by Professor Davis. 



