292 AXyALS yEW YORK ACADEMY OF >CIEyCE> 



the time since the last great glacial stage was not less than 31,uu0 years. 

 Gilbert. Uphani and other geologists of the United States Geological 

 Snrvev after pointing ont many sonrces of error in all snch ealcnlations 

 were inclined to the adoption of periods ranging from 6,000 to 10.000 

 years. Gilbert's sturey is the mos: careful which has been made; he 

 estimated (1896) that the gorge of Xiag^ara is not more than 7,000 years 

 of age. The Canadian geologist Spencer arriYed at a restdt almost iden- 

 tical with that of LyeU, namely, 32,000 years. 



The most careful estimates on the sub«iivisions of Postglacial time in 

 Europe are those of Penck (1909, p. 1168) which may be briefly sum- 

 marized as follows : 



IV, 2nd WtTBM AfAXiMFM. be^mning of Upper Palieo- 



litMc CTilrare 2i3.i)00 to .^.i^? rears 



Achen retreat, i>eriod. of Aurignaeean and Solutreaxi 



cultnre 



Buhl advance, period of early Magdalenian cnlture 



rXeiiscli • l^.r-oi^ - 24.0rn'> " 



Post-BtiliL period of late Magdalenian culture 10.00) '• 16.000 " 



Daun Stage. r»^ri":Mi of the close "f the Upi:»er Paln-<:»- 



litMc, Azilian culture 7.000 " 



Age of Copper in Euroj^e 4.<X)f3 - -djX-O 



According to Heim's*^ calculations the period since the deposition of 

 the Biihl moraines in the Lake of Lucerne amounts approximately to 

 16,000 years and if the Magdalenian culture deposits of this formation 

 are of the age of the Buhl advance we mfiy estimate with Xeusch that 

 the Biihl advance occurred at least 21,000 years ago. This advance is a 

 very important period because it represents the last of the Arctic, Tundra 

 and Steppe Faunas in central Europe prior to the establishment of the 

 modem forested conditions and fauna. 



Fauna of the Fourth Glacial Stage. — ^The severe climate of the rouri:h 

 Glacial Stage is indicated by the mammalian life found at Achenheim 

 and Sirgenstein associated with what is known as the "full Mousterian" 

 Palaeolithic culture (Schmidt. 1912). Here for the first time there is a 

 predominance of the Ttindra Fauna (fifteen species) as well as the ad- 

 vent of the Steppe Fauna (two species), while the Forest Fauna (seven 

 species) and Meadow Fauna (four species) are still represented. The 

 straight-tusked elephant (E. antiquus) and broad-nosed rhinoceros (D. 

 mercJ:li) have disappeared and are now replaced by the woolly elephant 

 (E. r.rirninpriiiL^') and woolly rhinoceros (D. antiquitatis) . The mam- 



*^ Heim. a. : "t'ber das absolute Alter der Elszeif' Vierteljahrsschrift der narur- 

 Corsch. Ges. in Zurich, Jahrg. -39. No. 2. pp. 1S0-1S6. 1S94. 



