158 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



There is also some evidence of unconformable deposition of the later 

 beds upon the Richmond. On the south side of the Clarendon Moun- 

 tains the Chapelton beds of the Cambridge formation rest directly 

 upon the Minho beds of the Blue Mountain Series, without the inter- 

 vention of the Richmond beds ; the Catadupa beds at Catadupa are 

 interpolated between the Richmond and Chapelton beds ; at other 

 places, on the north side of the island, the Chapelton beds rest directly 

 upon the Richmond. 



Furthermore, the older beds of the Blue Mountain Series, the 

 Cretaceous limestones and Richmond beds, are all turned up together 

 in this older and more complicated system of foldings, and inseparably 

 constitute the summits of the Blue Mountain Ridge, which between 

 the altitude of 3,000 and 7,325 feet now protrude 4,325 feet above all 

 the later Eocene and Oligocene formations. These facts, especially 

 the different nature of the folding, strongly suggest an interruption 

 of sedimentation and a corrugation of the strata after the close of the 

 Richmond deposition period, and also indicate that mountain making 

 movements were operative in Mid-Eocene time, which may have been 

 the initiation of the uplifts, which had far reaching importance in 

 Antillean history, accompanied by active vulcanism in the Isthmian 

 and probably Windward regions. We are not prepared to interpret 

 fully this particular event without further examination of the region. 

 If, on the other hand, this folding did not occur at this particular 

 epoch, then the Richmond beds may mark the initiation of a great 

 subsidence so clearly traceable in the succeeding epoch. 



Lime making fossils begin to appear in the upper part of the Rich- 

 mond shale where the Cambridge beds begin, — such as Foraminifera, 

 corals, and Mollusks, — and the lime they produce has been taken into 

 solution and segregated into masses and strata of nodular limestone, 

 occurring in the shale. These impure limestones of the Cambridge 

 beds represent the transition between the terrigenous littoral deposits 

 of the Richmond and the deep oceanic chalks of the Montpelier epoch, 

 and are a step in the great subsidence that was then progressing. 

 The "Yellow Limestones," like the Richmond beds, are undoubtedly 

 of Eocene age, corresponding to the later portion of that period. 



The rapidity with which the impure nodular limestones of the 

 Cambridge grade into Montpelier chalks, composed of Globigerinje and 

 void of molluscan fossils, indicates that the subsidence, initiated as above 

 stated, continued to profound depths, 1,200 fathoms or more, accom- 

 panied in adjacent localities with great deposits of Radiolarian earths. 



