THE OCEANIC CORAL ISLAND SUBSIDENCE. 407 
self; and greater along the Caribbean Sea parallel with Cuba, 
as well as along the Bahama reefs, than in Cuba. 
The conclusions of Mr. Thomas Bland, based on the distri- 
bution of terrestrial mollusks in the Bahama Islands, a sub- 
ject with which he had made himself familiar by study in 
the region, have much interest in this connection. He 
shows? that these mollusks, eighty in number of species, 
prove that the alliance of the Great Bahama Bank with 
Cuba is very close, as is apparent in the many species of 
Polymeta and Strophia, and the occurrence in both of the 
genera Polygyra, Thelidomus and Melaniella, not known in 
Hayti; while Turk Island bears evidence of connection with 
Hayti through the genus Plagioptycha and the species com- 
mon to the two, P. Albertsiana and P. disculus. 
After mentioning the views in this volume on the dimin- 
ished size of the islands to the eastward and the evidence 
thereby of subsidence, he says : — 
“The facts regarding the diminution in size of the islands 
of the West Indies to the eastward are of peculiar interest, not 
only as affording conclusive evidence of greater subsidence in 
that direction, but also in connection with geographical distri- 
bution. The banks and islands forming the long Bahama 
chain diminish in size to the southeast, where are situated at 
its termination the submerged Mouchoir Carré, Silver and 
Navidad Banks. In a similar manner, the submerged Virgin 
Island Bank (with Anegada on its northeastern extremity 
geologically resembling the Bahamas in the opinion of Dr. 
Cleve), Sombrero and the Anguilla Bank, terminate the chain 
of the West Indies eastward from Cuba, parallel with the Ba- 
hama chain. In the caves of Anguilla the remains of large 
1 Annals of the Lyceum of Natural History of New York, Vol. X., 1873, an 
abstract of which appeared in the American Journal of Science, 1874, VIII. 231. 
