HILL: GEOLOGY OF JAMAICA. 170 



mation may be about 200 meters. The formation of the yellow limestone, 

 essentially marine in character, seems to have been terminated by river-mouth 

 deposits, since its highest strata consist of shells and carbonated clay slates, 

 containing brackish water. At this period the formation must have been almost 

 on a level with the surface of the sea, but after it, during the deposition of the 

 white limestone, there was presumably a great epoch of depression ; the yellow 

 limestone must have descended to considerable depth to allow the formation of 

 800 meters of white limestone. A remarkable peculiarity becomes apparent at 

 the surface of the yellow limestone. After the primitive forest has been cut 

 down, no other trees grow on it, but only a graminea {Anatherum bicorne). 

 This phenomenon is so characteristic that it indicates the boundaries of this 

 formation. Owing to the extraordinary porousness of the white limestone, 

 water readily seeps through it, and, unless carried off by underground flow, it 

 descends until it reaches the impervious clay of the yellow limestone, and there, 

 under appropriate conditions, gushes out of the ground. 



" Among the common fossils of this formation are Cardium, Ostrea, Trochus, 

 Natica, Cerithium, Conus, Serpula, Echinocyamus, Echinolampus, Orbitoides, 

 and Corals." 



Every detail above noted corresponds exactly with the character of the 

 Cambridge beds of Jamaica. 



Formations allied to the deep water Montpelier beds of Vicksburg age 

 (late Eocene of old writers, early Oligocene of Heilprin and Dall) con- 

 stitute an especially important landmark in Antillean history, and have 

 wide occurrence. White limestones made up of Globigerina chalks or 

 white siliceous deposits composed of Radiolaria occur in Cuba, Haiti, Bar- 

 bados, and Trinidad. In Barbados the Globigerina chalks grade down 

 into pure Radiolarian earths, constituting with them a related and con- 

 tinuous formation, which in turn overlies the older Eocene Scotland for- 

 mation, composed of land derived sediments like the Richmond beds, 

 and are folded together with them in the most complete mountain struc- 

 ture. This association of the Globigerina and Radiolarian beds in Bar- 

 bados establishes the intimate relations of the deposits. 



At Baracoa in the northeast part of Cuba, and Port Jeremie, on the 

 north coast of the southeastern peninsula of Haiti, Radiolarian earths 

 occur in great abundance. I was so fortunate in my explorations of 

 Cuba as to ascertain the exact stratigraphic occurrence of these Radiola- 

 rian earths unconformably beneath the late or Bowden Oligocene, then 

 called Miocene by Dall.^ In the light of my later researches iu Jamaica, 



1 Notes on the Geology of the Island of Cuba, Bull. Mus. Comp. Zool., Vol. 

 XVL No. 15, Cambridge, 1895, p. 253, PI. I. Fig. 5. 



