hill: geology of Jamaica. 123 



With this exception not a single species of the fauna lias been reported 

 from the North or South American Mainland. Probably the same fauna 

 occurs in Cuba and Haiti, judging from papers by G. F. Matthew^ and 

 Tippenhauer.^ It is also possible that it may occur in Guatemala and 

 Costa Kica, or even -Southern Mexico, where large unstudied Rudistean 

 faunas abound. As "will presently be noted several of these species of 

 Rudistes also occur in the overlying Eocene (Cambridge) beds. 



The most numerous and conspicuous forms of the Jamaican Creta- 

 ceous fauna are genera which proportionately have but slight representa- 

 tion in the North American Cretaceous, such as the corals, Rudistes, 

 Nerinsea, and Actaeonella, while on the contrary there seems to be an 

 almost entire absence in the Jamaican fauna of such forms as Ammo- 

 nites,^ Trigonia, Gryphcea, Exogyra, Brachiopoda, and Echinodermata, 

 which are so characteristic of the North and South American Cretaceous 

 of Atlantic sedimentation. The Jamaican Cretaceous fauna, which is 

 the oldest known life of the Great Antilles, is unique. Several Rudistes 

 and two species of corals from these supposedly Cretaceous formations 

 continue upward into the beds which are here placed in the Eocene, in- 

 dicating a gradation of the faunas of these two epochs, as further dis- 

 cussed on a later page. It may possibly be explained upon the hypothesis 

 that it lived adjacent to an insular land, separated from the continent 

 by great depths of oceanic water which prevented migration to it of the 

 main littoral fauna in its eiitirety. These beds represent the expiring 

 days of the Cretaceous and can hardly antedate the Senonian in age. 



The Eocene Faunas. 



The existence of Eocene strata in Jamaica has hitherto been a ques- 

 tion difficult to determine owing to the previous confusion of knowledge 

 of the stratigraphy and paleontology. It is our opinion that the Eocene 

 is well represented by at least two distinct formations, the Richmond 

 and Cambridge, and by three, if the Montpelier formation, which is the 

 equivalent of the Vicksburg stage, is included in the Eocene, as has 

 been customarily done by all American writers until recently, when 

 Heilprin and Dall, following Conrad, have again placed the Vicksburg 

 in the base of the Oligocene. 



1 Canadian Naturalist, 1872, Vol. VIT. p. 19. 



^ Die Insel Haiti, Leipzig, 1893, See Plate preceding page 881. 



8 Ammonites have been reported in one locality only in Jamaica (page 78), 

 but their occurrence there has not been verified or accepted by the paleontologists 

 of the Survey. 



