332 T. C. CHAM BERLIN 



The paleobotanical evidence has been interpreted as implying 

 a much shorter period than do the mammahan remains between 

 the lower and the upper deposits of the creek series. The general 

 presumption of changeableness, however, has commonly been 

 held to favor the mammals. 



Marine paleontology seems to be rather neutral in this war of 

 criteria. Th^ marine layer that underlies the beach ridge in which 

 'the creek sank its valley and later began to fill it contains few 

 fossils, if any, of species other than those now living. Using the 

 inherited organic criteria, the age of this layer has usually been 

 placed at or near the end of the Pleistocene Period. It would seem 

 to be a fair accommodation to the general tenor of the various 

 evidences to make the last retreat of the sea from the mainland 

 in the Vero region the beginning of the Recent Period. Such a 

 reference, however, places the beginning of the creek deposits 

 within the Recent Period. This conforms very well to the 

 apparent requirements of regional geology, of physical geology, of 

 anthropology, and of archaeology. Perhaps paleobotany might be 

 accommodated to it without putting its data under much strain 

 if any at all; but vertebrate paleontology, especially mammalian 

 paleontology, as heretofore understood, would apparently need 

 radical revision. The suggestion here implied, that the extinct 

 mammals may have lived on even into the Recent Period, goes a 

 step farther than the suggestion made at the conferences to the 

 effect that the several vertebrates heretofore only known to occur 

 in Early or Middle Pleistocene beds really lived on in this south- 

 ern clime until a much later Pleistocene date. Even then it is 

 not necessary to suppose that the older of these extinct mammals 

 were contemporaneous with man, for the two hundred centuries 

 assigned to the Recent Period give room for appreciable differen- 

 tiation. Obviously this basis of reconciliation throws the burden 

 of revision most heavily on vertebrate paleontology and subordi- 

 nately on paleobotany. 



Those who are thus hypothetically made to bear nearly the 

 whole burden of revision are entitled to trial hypotheses which 

 shall in a like hypothetical way throw the burden of revision on 

 other criteria. The method of multiple working hypotheses, in 



