[pBNHALLovv] NOTPZS ON TERTIARY PLANTS 67 



hundred feet above the sea, down to, and occupying the lowest valleys 

 at less than one hundred feet. 



In dealing wdth the possible age of these deposits, Dr. Spencer 

 makes no distinction between the Lafayette and the Columbian, thereby 

 dissenting from the opinion of Mr. W. J. McGee, which he quotes to 

 the effect that the Lafayette belongs to the Pliocene or later Miocene, 

 while the Columbian is Pleistocene, though he agrees with Mr. McGee 

 that the Pleistocene period commenced earlier in the south than in 

 the north, leaving its records in the Lafayette deposits.^ 



A more recent discussion of these formations by Mr. E. Ries ^ 

 nevertheless adopts the views of Mr. McGee, placing the Lafa3''ette in 

 the late Miocene (Neocene) and the Columbian in the Pleistocene. 

 Further careful inquiry has established the fact that there is practi- 

 cally no available knowledge \\hich may be utilized. in determining the 

 age of the deposits in question, and it therefore becomes of the greatest 

 importance to ascertain what conclusions may be derived from the 

 occurrence of the common tamarack at such an uuusual place. 



The occurrence of Larix americana in the Dahlonega clays at a 

 point so far distant from its present southern limit at once suggests 

 that the deposits are of Pleistocene age. That they are not of more 

 recent origin would seeim to be supported by the complete absence of 

 Larix from the same region at the present time; whilst it would seem 

 improbable that they are older, because W'e as y-et have no knowledge 

 of tlie wood of this tree in deposits of greater age than the Interglacial. 

 Within Pleistocene time, Larix americana is one of the most abundant 

 and characteristic types within a wide geographical range, extending 

 from Montreal through the region of the Great Lakes westward to the 

 Moose River in Canada, and to Fort Madison in lowa.^ It has also 

 been found in peat bogs in New Brunswick, but as such deposits are in 

 all prnl)ability of very recent origin, they possess no significance for 

 our present purpose. 



Somewhat extended investigations of the Pleistocene deposits in 

 the Don Valley at Toronto have already given us somew^hat detailed 



'■ Since the above was Avritten. Mr. W. S. Yeates, Director of the Geological 

 Survey of Georgia, has kindly directed my attention to a reference in his report 

 upon the Gold Deposits of Georgia (Bull. No. 4_A., pp. 293 and 395) to the 

 formation in which the wood was found, from which it appears that Dr. Knowl- 

 ton (1896) had already referred it to the Pleistocene, while Dr. Becker referred 

 it more specifically to the Columbia formation. It would therefore appear that 

 the same conclusion has been reached from two di.^tinct and independent points 

 of view. 



- Maryland Geol. Surv.. 1902, p. 379. 



• Jn'l. Geol. III., 636 : Bull. Geol. Soc. Amer., I., 326, 334 : Pleist. Flora of 

 Can., B.A.A.S., 1898 & 1900 . 



