Vol. VII] DICKERSON— ANCIENT PANAMA CANALS 201 



His statement concerning the Atlantic affinities of this fauna 

 receives strong support when the gastropods and pelecypods 

 are studied as well. All the coral genera recognized in this 

 assemblage except one occur in the Bowden or associated hori- 

 zons. His conclusions concerning the Pliocene age of these 

 beds rests upon the infirm basis of comparison with a Pliocene 

 coral fauna from Florida. Conrad in Volume 5 of the Pacific 

 Railroad Reports, says that "the Ostrea vespcrtina, Anomia 

 subcostata, and Pecten deserti occurring in the banks of Carrizo 

 Creek are unlike any recent forms that I am acquainted with 

 from the Pacific Coast, but analogous to Miocene species of 

 Virginia. This formation may therefore be regarded as of 

 Miocene origin." Conrad's early recognition of the Atlantic 

 facies in this fauna and his conclusions concerning its age 

 appear to the writer to be essentially correct. Spencer and 

 Vaughan's conclusions concerning Pliocene connections be- 

 tween the Atlantic and Pacific appear very doubtful. This 

 problem will be discussed at length in another paper. 



The Bowden fauna which typically occurs in Jamaica is very 

 widespread and the relationship between the recent Panamic 

 fauna and the Bowden fauna is an intimate one. The wide 

 spread submergence of the Antillean lands is also evidence 

 which points to the occurrence of shallow connections at least 

 through the two isthmuses during the Miocene. This submer- 

 gence was so great at this stage that most of the Antillean 

 islands were vastly decreased in area. 



The recent discovery of Merychippus,^- a horse character- 

 istic of the Miocene, associated with other Miocene vertebrates, 

 in the Alum Bluff formation of Florida, a Bowden equivalent 

 or associated horizon, gives us conclusive proof of the Miocene 

 age of these beds. 



According to Professor J. C. Merriam,^^ this species of 

 Merychippits represents essentially the same stage in evolution 

 as one of the recently discovered horses of the Tehachapi 

 Mountains region of California. These continental deposits 

 of the Tehachapi Mountains according to Merriam and 

 Buwalda, represent middle Miocene or the upper portion of the 

 lower Miocene. Evidently these two faunas will prove of 



"= Sellards, E. H., Eighth Annual Report, Florida Geological Survey, 87-88, 1916. 

 " Merriam, J. C, in Eighth Annual Report, Florida Geological Survey. 88, 1916. 



