The Cretaceous and Tertiary Question in Jamaica. 425 



formations continue upward into the beds which are here placed in 

 the Eocene, indicating a graduation of the faunas of these two 

 epochs." And, further on, " In view of the facts presented, the 

 writer finds it utterly impossible to accept the ' rolled ' hypothesis, 

 and he can see no way of avoidiiag the positive conclusion that the 

 Rudistean forms in the Cambridge beds represent a survival of 

 Cretacedus tyj)es into the Lower Eocene " ; and referring to the 

 fossils, he remarks : " As a fauna nothing exactly analogous to it 

 is known elsewhere." 



These observations lead Hill to the conclusion that " the discovery 

 of the Cambridge formation gives a certainty to the existence of an 

 Eocene system in Jamaica, aggregating at least 1,500 feet in thick- 

 ness " ; and, further, that " the palaeontologic peculiarities of the 

 Richmond and Cambridge formations, analogous to those of the 

 preceding Cretaceous beds, are such as can only be accounted for 

 by geographic environment, and point to early insularity of the 

 island through Eocene time." 



Referring to the Richmond beds, Hill says : " The presence of 

 supposedly Cretaceous Rudistean genera would ordinarily invalidate 

 the data upon which the Eocene age of the Richmond beds hitherto 

 depended for establishment, were it not for our positive evidence 

 to be presented that these forms arc found in situ in overlying beds, 

 associated with undoubted Eocene fossils." 



The conclusions that Hill arrived at led him to publish a map, 

 compiled from the map of Sawkins and Brown with additional 

 data, which contains several alterations, and in which great 

 prominence is given to the " Cambridge " formation. With all due 

 respect to Hill and the work he accomplished in Jamaica, I cannot 

 regard this map as at all an improvement on the old English survey 

 map of Sawkins. 



The matter is thus one of far-reaching importance in connexion 

 with Antillean geology, and so, perhaps, I may be excused if I give 

 the results of my examination of the sections in question. 



As regards the Richmond beds of Hill, which correspond with 

 the beds mapped by Sawkins as Carbonaceous shale or Black 

 shale, the examination of several sections of these beds near Port 

 Antonio, at and near Port Maria, and elsewhere in Jamaica, led me 

 to conclude that the pieces of Cretaceous limestone and the rolled 

 Rudistce that occur among the conglomerates in these beds are 

 all derived from the denudation of older formations. They are 

 exactly analogous to the pieces of Carboniferous limestone in the 

 Permian Brockrams of England, and, in fact, some of the Cretaceous 

 limestones of Jamaica had already been semi-marmorized before 

 they and several varieties of gneisses and other rocks not now seen 

 in situ in Jamaica were incorporated in the Richmond beds. The 

 Eocene fossils that occur among the Richmond conglomerates at 

 Port Maria and elsewhere are all either fresh or only slightly rolled 

 and broken, and were clearlv living at the time the beds were 



