474 STEPHEN SARGENT VISHER 



midst of it, we may follow Penck.^ The mammalian fossils seem 

 to him to prove that the loess was formed while boreal animals 

 occupied the region, for they include remains of the hairy mammoth, 

 woolly rhinoceros, and reindeer. On the other hand, the typical 

 interglacial beds not far away yield remains of species characteristic 

 of milder climates, such as the elephant, the smaller rhinoceros, 

 and the deer. In connection with these facts it should be noted 

 that occasional remains of tundra vegetation and of trees are found 

 beneath the loess, while in the loess itself certain steppe animals, 

 such as the common gopher, or spermaphyl, are found. Penck 

 interprets this as indicating a progressive desiccation culminating 

 just before the oncoming of the next ice sheet. 



The evidence in favor of the hypothesis that the loess was 

 formed during the maximum extension of the ice chiefly concerns 

 its relation to the ice sheets and to the streams which flowed from 

 the melting ice. If the great American deposits of loess do not 

 represent the outwash from the lowan ice, there is little else that 

 does, and presumably there must have been outwash. Also the 

 distribution of loess along the margins of streams suggests that 

 much of the material came from the flood plains of overloaded 

 streams flowing from the melting ice. Furthermore, in many 

 places at least, the drift just beneath the loess presents little or 

 no evidence of having been weathered or leached before the loess 

 was laid down. ChamberHn found that many tests showed it to 

 contain about as much calcareous material as the loess itself. 

 This suggests that it was laid down at about the same time as the 

 underlying drift, not notably afterward.^ Likewise, although 

 Shimek has emphasized the fact that most of the snails do not show 

 depauperization, McGee reports that depauperization is evident 

 among those found near the glacial margins, and that shells are 

 very rare there. Both of these conditions suggest that much of 

 the loess accumulated under glacial conditions. 



Thus although there are some points in favor of the hypothesis 

 that the loess originated (i) in strictly interglacial times, (2) at 



^ Penck's conclusions are given in full in W. B. Wright, The Quarternary Ice Age, 

 London, 1913. 



^ T. C. Chamberlin, personal communication. 



