116 PROCEEDINGS OF THE PALEOXTOLOGICAL SOCIETY 



frequently among the various species of Sigillaria and Lepidodendron. The 

 author here calls attention to the remarkable resistance to decay of the bark 

 of the common birch and the equally striking susceptibility to decay of the 

 wood of this tree. Consideration of the differential rate of decay of the bark 

 to the wood of the birch throws much light on the process which has so often 

 produced the kind of fossilization represented by the sand-filled bark of Lepido- 

 dendron. It appears most probable that the dark cylinder of the Carboniferous 

 lycopods were generally hollowed out by rapid decay of the wood and then 

 filled with sediment before fossilization began, just as the empty birch bark 

 of the trunks are now being prepared for fossilization in Canadian lakes and 

 rivers. 



PRELIMINARY CORRELATION OF THE CRETACEOUS AXD TERTIARY FLORAS 



OF ALASKA 



BY ABTHUB HOLLICK 



(Abstract) 



Previous to the year 1902 little or nothing was known in regard to the Cre- 

 taceous flora of Alaska. During that year A. J. Collier, of the U. S. Geological 

 Survey, made collections of fossil plants at several localities in. the lower part 

 of the Yukon River Valley, and in the following year further collections in the 

 same region were made by the writer. The plants included in certain of these 

 collections proved to be Cretaceous in age, and subsequent collections by other 

 field parties of the Survey elsewhere in the territory indicated the presence of 

 a Cretaceous flora at a number of other localities. 



The Tertiary flora, first mentioned briefly by Grewingk in 1850, was subse- 

 quently found at many localities in the southern part of the territory and was 

 described by Goeppert in 1861, Heer in 1868 and 1869, Eichwald in 1871, Lesque- 

 reux in 1883, Newberry in 1883 and 1898, and Knowlton in 1904. The writer 

 also discussed it briefly in 1911. 



Little or no attempt was made, however, to correlate the Tertiary floras of 

 the different localities, and all were generally classed as "Arctic Miocene" in 

 age — now recognized as Eocene. 



In 1892 Dall and Harris proposed the name "Kenai" as a group name for 

 certain Tertiary strata exposed at Katchemak Bay, Kenai Peninsula, and that 

 name has since then been more or less loosely applied to a number of different 

 beds in which Tertiary plants were identified. 



A critical examination by the writer during the past two years of collections 

 from about one hundred and fifty localities has resulted in the differentiation 

 of the typical Kenai flora, which is Upper Eocene in age ; a Lower Eocene flora 

 which is well exemplified in collections from the Hamilton Bay region of Ku- 

 preanof Island, and at least two of Cretaceous age, represented in collections 

 from localities in the lower Yukon Valley and the Alaskan Peninsula. 



The scope of this paper includes a preliminary correlation of the floras, 

 characteristic species of each, localities, and bibliography. 



At 4.15 the Society adjourned. 



