hill: geology of Jamaica. 127 



duerdeni. The association together of species of Styloccenia and Stylo- 

 phora^ both being close to Eocene species of Europe, would make the 

 probabihty in favor of the Eocene age of the beds. Therefore the paleon- 

 tologic evidence, though not conchisive, supports the opinion of Duncan 

 regarding the age of the beds. Fortunately the stratigraphic position of 

 the Richmond beds is clearly made out, independent of the fossils, so ni 

 this case positive paleontologic proof is not essential for determining 

 their position. We studied the locality of Port Maria from which these 

 corals came in order to ascertain their stratigraphic position, which beyond 

 doubt is that of the typical Kichmond beds. 



Etheridge ^ mentions the occurrence of fossil Rudistes in these beds, 

 but suggests in explanation that their presence might be accounted for 

 upon the hypothesis that they could be water-rolled survivals of the 

 denudation of the lower lying Cretaceous beds. Whether the specimens 

 of " Hippurites," Radiolites, and Actseonellas noted are indigenous to these 

 particular beds or not, we cannot state, not having been so fortunate as 

 to find any of the fauna in situ. We question the conclusion, however, 

 that they are derived specimens, because similar forms of Rudistes at 

 least were found by us in situ in the overlying Cambridge beds, as will 

 be shown presently. It is probable, as shown in the Ballard bed of the 

 Minho section, that these Rudistean forms appeared in sporadic colonies 

 throughout the thickness of the black shales of the Minho and Richmond 

 beds, and continued into the Cambridge formation. Whoever undertakes 

 the further study of these beds must remember that specimens of free and 

 well preserved Rudistes should not be confused with the rolled pebble of 

 hard crystalline limestone of the Jerusalem type which should also occur. 



The presence of the supposedly Cretaceous Rudistean genera would 

 ordinarily invalidate the data upon which the Eocene age of the Rich- 

 mond beds hitherto depended for establishment, were it not for our 

 positive evidence to be presented that these forms are found in situ in 

 overlying beds, associated with undoubted Eocene fossils. The other 

 species are all of Eocene facies and point to their Eocene age, which 

 conclusion we are able to fix with positiveness by the evidence of the 

 overlying Cambridge beds, where a similar mixture is found, whose true 

 nature has hitherto escaped observation. 



The Cambridge Formation. 



From a paleontologic standpoint these beds mark one of the most 

 interesting and valuable horizons in the whole Jamaican sequence, 



1 Jamaican Reports, p. 311. 



