338 PROCEEDINGS OF THE ACADEMY OF [April, 



Gatun species identical with those of Santo Domingo 22 



Gatun species identical with those of Bowden 13 



(Eight of the species are common to the Santo Domingo and 



Bowden beds.) 

 Gatun species more closely allied to those of Santo Domingo and 



Bowden than to any other known forms 20 



Gatun species identical with those of Chipola 4 



Gatun species identical with recent forms 6 



Gatun species as yet known only from that formation 67 



It will be noted that at least 40 per cent, of the 104 Gatun species 

 now known are either identical with, or very closely related to, Santo 

 Domingo forms. A considerable proportion of the remaining species 

 are certainly allied to those of Santo Domingo, but without exhaustive 

 studies of the groups, their nearest affinities cannot readily be deter- 

 mined. 



Of the 6 species identical with recent forms, 4 are Antillean, one 

 inhabits both coasts and one the Pacific coast only. It is obvious 

 that in the Antillean and Isthmian Oligocene the ancestral stocks 

 of a large part of the modern Antillean and Panamic faunas are present, 

 genera now characteristically Panamic being especially well-developed, 

 such as Cymia, Solenosteira, Strombina, Malea, Trachycardium of the 

 belcheri group, dementia, Acila, Tesseracme, Cadulus of the dentalinus 

 group, etc. None of them are deep-water forms, and all are absent 

 or rare in the curiously impoverished littoral Antillean fauna of the 

 present time. 4 



In the following list we have included all species reported from the 

 Gatun beds. Species marked with an asterisk (*) were not included 

 in the collections we have studied. With a few exceptions noted in 

 the text, the other species listed are in the collection of the Academy. 



Acknowledgments are due to Professor Win. B. Scott and Mr. 

 Gilbert Van Ingen for the privilege of studying a small series of Gatun 

 specimens in the museum of Princeton University, collected in 1908 

 by Mr. Ward H. Farrington. We would also acknowledge the courtesy 

 of Dr. Wm. H. Dall, in giving access to material in the U. S. National 

 Museum. 



Genera reported by Toula and Hill without specific identifications 

 have not been inserted in the following list. 



4 Hill's statement (Bull. Mus. Comp. Zool., vol. 28, p. 265) that Pacific forms 

 do not exist in the Antillean Oligocene is clearly at variance with the facts. 

 An important element in the littoral fauna of the Panamic province is directly 

 traceable to Antillean Oligocene faunas, as the above list demonstrates. 



