1894. rROCEEDlNGS OF THE NATIONAL MUSEUM. 447 



Antilles slioukl develop into the group Gaprinns^ not a species of wliicli 

 slionld be found north of this archipehigo, and that not one of the six 

 other Greater An tillean groups should be represented in the Windward 

 Isles ; that it shoukl develop a few species on the mainland and i)ass into 

 Labyrinthns., no species of winch is found outside the continent. 



It appears to me a not unreasonable sohition of this rather curious 

 phase of distribution, in view of the very slight relationship that other- 

 wise exists between the land and fresh-water mollusks of the Greater 

 and Lesser Antilles, and of the fact that many of the latter islands are 

 of such recent date, that it is more probable that ancestral forms of 

 Pleurodonte migrated from Jamaica across the old landway to Honduras; 

 that the subsidence of some 400 miles of this ancient bridge destroyed 

 the connecting links so that Pleurodonte restricted dexeloped in the 

 island and Lahyrinthus on the continent; that the latter (extending 

 now as far north as Central America) spread out over the lower regions 

 of northern South America, and developed into Isomeria in the moun- 

 tains; that from this stock descended Ca2)rinus, which is now repre- 

 sented by a few species in Guiana, and probably in the adjacent terri- 

 tory, ana which migrated northward among the Lesser Antilles to St. 

 Kitts and Barbnda, its farthest limit.* 



To briefly recapitulate, a considerable portion of the land snail fauua 

 of the Greater Antilles seems to be ancient and to have developed on 

 the islands where it is now found. There appears to be good evidence 

 of a general elevation of the Greater Antillean region, probably some 

 time dnring the Eocene, after most of the more imjwrtant gronps of 

 snails had come into existence, at which time the larger islands were 

 united, and there was land connection with Central America by way of 

 Jamaica and possibly across the Yucatan Channel, and there was then 

 a considerable exchange of species between the two regions. At some 

 time during this elevation there was probably a landway from Cuba 

 across the Bahama plateau to the Floridian area, over which certain 

 groups of Antillean land mollusks crossed. At this time it is likely 

 that the more northern isles of the Lesser Antilles, which seem to be 

 volcanoes of later Tertiary and Post Pliocene date, were not yet ele- 

 vated above the sea or if so they have probably been submerged since. 

 After the period of elevation there followed one of general subsidence.! 



" Clstula, wbicli has its metropolis in the Greater Antilles, has a somewhat similar 

 distribution. Several species are found in Mexico, Central and northern South Amer- 

 ica, with one species in Trinidad, but not north of that until we reach Antigua, near 

 tho upper end of the chain. Neociiclofiis, with a great development in the more 

 northern archipelago, is also abundant on the continent, and is found in the Lesser 

 Antilles as far north as Martiuicjue; and CoJohostylus, with a similar distribution, 

 extends northward only into Trinidad. 



t. lust how extensive this disturbed area was can not now be told. It is well known 

 that along the north shore of Cuba, back of Matanzas and Havana, there are raised 

 beaches, some 1,200 feet above the sea, which have been supjiosed to be recent, but 

 Mr. B. T. Hill, of the U. §. Geological Survey, who has recently visited the island 



