HILL: GEOLOGY OF JAMAICA. 219 
This orogenic elevation most probably united the Antillean lands, 
constructing bridges for the wide distribution of the ancestral forms of 
the wonderful land shell faunas of the Antilles from Central America 
to Guadeloupe, which are first found fossil in the succeeding Bowden 
formation. It also brought the submerged bottoms up to a height 
sufficient for the habitation of littoral Mollusca, and permitted them 
to migrate for the first time from the continental margins to the 
islands, and to attain wide West Indian distribution. The preceding 
marine faunas of Jamaica, at least of the Antilles, had been all insular 
and unlike that of the continental margins. 
There are no geologic data to prove or disprove connection between 
the expanded mountainous Antillean lands with the main continent 
other than that a marine passage between the Gulf and the Atlantic 
continued across northern Florida. The absence in the Antilles of 
remains of continental vertebrates of this period, or living descendants 
thereof, would indicate that no such connection existed. Furthermore, 
the distribution of the land shells show that tho Equatorial current was 
flowing into the Caribbeau through breaks in the windward rims. 
During this epoch the Caribbee voleanoes, persisting from the previ- 
ous Eocene epoch, were in superb activity and undergoing their maxi- 
mum development along the western border of the eastern limb of the 
submerged plateau which may have been the remnant of the probable 
bridge or Archipelago of Jurassic time. 
The history of the western Gulf region during this epoch of Antillean 
uplift is obscure. Hilgard * has noted the absence, west of the Missis- 
sippi, of Tertiary deposits of later age than the Vicksburg, and con- 
eluded that the Gulf must have been closed on the eastern side. The 
probable absence from the surface west of Red River of marine deposits 
of late Oligocene and Miocene age,? and the presence of apparently 
fresh water formations in their place along the Texas coast, may seem 
favorable to this conclusion, but further study is much needed. 
The evidence supporting a contrary hypothesis is of a few alleged old 
Miocene Gasteropods from a depth of some 3,000 feet, in the borings of a 
well at Galveston, which Harris alleges have Pacific affinities, No out- 
Cropping strata have as yet been discovered to support this purely pale- 
ontologic hypothesis. 
However deficient may be our knowledge of the extent and details of 
1 Geological History of the Gulf of Mexico, pp. 0, 7. 
2 The late Tertiary and Pleistocene history of the Texas Coastal Plain has not 
48 yet been fully studied or interpreted. 
