1897-98]- LATE FORMATIONS AND GREAT CHANGES OF LEVEL IN JAMAICA. 339 



tion (except the inclusion of volcanic rocks), as the underlying uncon- 

 formability is apparent, and also the occurrence of another uncomform- 

 able series overlying its eroded surface. 



A few poorly preserved fossils have been found in the marls 

 apparently belonging to modern species of Cai'diuni and Ostrea. In 

 the volcanic beds some remains of fossil trees occur along the coast. 



At Port Antonio, on the terrace where the town is built, the upturned 

 strata of White Limestone are succeeded by a bed of yellowish-white 

 marl, from two to five feet in thickness, containing rounded pebbles 

 which occur in the Layton series. (Figure 2, Plate III). 



Two or three miles west of the old Low Layton volcano. Great 

 Spanish River enters the sea after having excavated a valley more than 

 a mile wide in the coast range of mountains. Here the greatly eroded 

 hillocks of gravel and loam rise from 40 to 100 feet above the sea. 

 The gravel often occurs only as layers scattered through the loam. 

 The beds may undulate and dip at as much as five degrees, or the 

 undulations are similar to those in the Layton marls. They lie upon 

 the older eroded surface as do the marls, but in places even the White 

 Limestone was entirely removed before their deposition. These gravel 

 beds have apparently the same age as the marls, being equivalent to the 

 calcareous accumulations, at localities where the streams have brought 

 down the mechanical debris. The same phenomenon of the replace- 

 ment of the mechanical marls by gravel where the materials are 

 derived from the valleys, is a frequently recurring feature. 



Two sources of difficulties arise in identifying the Layton formation ; 

 (rt), when the unconformity between the White Limestones and the marl 

 is not observable, the one formation may be mistaken for the other, 

 but this is in part corrected by the common inclusion of rounded 

 pebbles in the Layton marls whether of limestone or some silicious 

 rock, a character that docs not commonly belong to the White Lime- 

 stones ; [p), when the unconformity between the Layton loams and 

 gravels with the overlying mechanical deposits of the same character 

 is not shown, there is a liability to error, but this is often corrected by 

 the appearance of the greatly eroded surfaces, or even only fragmentary 

 remains of the Layton gravels, for the denudation since the deposition 

 of the newer gravels, to be noticed hereafter, has been comparativcl)' 

 slight. This later degradation of the land forms an important feature 

 to be noticed again. 



Some half a dozen miles east of Kingston, the Hope River canyon 



