122 Part IL Chapter ı. 
mained above the sea to form a series of small islands during the second: 
quarter of Tertiary history. In the third quarter, another revolution occurred 
by which the floor of the ocean was corrugated into land, and the old sedi- 
ments with the deep sea muds and chalks were folded into the gigantic 
Antillean mountain systems, which at this time probably reared their summits 
to an elevation of twenty thousand feet and over, connecting all the Antilles 
into a single body of land. Another general subsidence followed in the last 
quarter of Tertiary time. It was sufficient to break up the Antillean land 
mass into the present island groups. During this the island of Jamaica, as 
the character of the land-snail fauna shows, as well as the depth of the 
channel between it and Haiti was first to be isolated, then Cuba, and after- 
wards Santo Domingo and Puerto Rico were separated. The connection 
between the Antilles and the mainland was broken and the Bahaman region 
was submerged. The subsidence continued until only the summits of the 
Antillean Mountains remained above water. Then followed another period of 
elevation which has lasted until the present. The Bahamas have emerged 
above the sea, either by elevation or growth, and have been tenanted by forms 
drifted from Cuba and Santo Domingo, while some have colonized recently in 
south Florida. There is, however, no reason to suppose that the two great 
basins the Gulf of Mexico and the Caribbean Sea, at any time lost their 
general integrity, or connection with the ocean, although their limits were 
altered and although at times the Pacific probably invaded. 
Collectively the Greater Antilles, from a physiographic standpoint, consist 
of a disconnected chain of mountains with an east-west trend. The 
highest peaks of this system in Haiti, Cuba and Jamaica are 10,300, 8000 and 
7000 feet respectively. The higher mountains above 2000 feet are composed 
of non-calcareous clay and conglomerate, largely the debris of unknown lands 
of pre-Tertiary time, which were buried beneath the sea in early Tertiary time 
to be lifted up later covered by a vast accumulation of oceanic sediments, 
which compose the white limestones which constitute the chief formations of 
the islands and occur in horizontal benches or terraces. Instrusions of igneous 
rocks, granite porphyry and basalt are found. 
A more or less continuous chain, the Antillean Mountains ,‚ extend in 
a westward direction from St. Thomas through Puerto Rico, Santo Domingo,, 
the northwest cape of Haiti, the Sierra Maestra range of Cuba to run beneath 
the sea in the Misterosa Bank of the Caribbean Sea. Santo Domingo is the, 
center of the island chain reaching in Mount Tina an altitude of 10,300 feet 
(3140 m). The Sierra de Cibao is the principal range in the island. It is 
flanked on the north by the Monte Christi range with an outlier toward the 
southwest and by a fourth mass of tall mountains which from the axis of the 
southwestern peninsula in Haiti. The latter extends toward Jamaica and is 
continued through that island as the Blue Mountains in Honduras. The north 
branch is a part of the main, or axial range which is represented in Cuba 
by the lofty summits of Sierra Maestra, bordering on the Santiago coast of 
