328 NATURAL HISTORY BULLETIN. 



the Mississippi Valley," published in 1885, and that of McGee 

 on "The Pleistocene History of Northeastern Iowa," published 

 in 1891. 



The cautious, conservative statements of Chamberlin and 

 Salisbury scarcely warrant the declaration that they "leave no 

 doubt" as to the fluviatile origin of the greater part of the 

 loess. Furthermore, at least one of the authors, Dr. Cham- 

 berlin, has materially modified his views concerning the loess 

 since the publication of the work cited. 



The splendid work of McGee, like that of Chamberlin and 

 Salisbury a classic in glacial literature, had for its purpose the 

 presentation of fundamental facts and conclusions bearing on 

 glacial phenomena. If we omit loess from the series of de- 

 posits discussed therein, the conclusions still remain of great 

 value. It is a fact long established that the loess forms a 

 mantle pretty uniformly covering the underlying deposits of 

 drift, etc., especially in eastern Iowa, and that, therefore, the 

 so-called "loess-topography" is really drift-topography. If the 

 loess could all be removed, the underlying drift would present 

 essentially (though not exactly, especially along the Missouri 

 river,) the topographic features of the present surface. The 

 altitudes of the more broken regions would be relatively less, 

 as the loess is usually thicker in hilly country. Whatever, 

 then, is prominent or striking in the topography of the pres- 

 ent surface, was at least approximately equally striking in the 

 post-glacial surface before loess was deposited upon it, and 

 many of the peculiarities in the structure and distribution of 

 these underlying deposits were well elucidated by that author, 

 and are in no wise affected by dissent with the inclusion of 

 the loess. 



In justice to Professor McGee it should also be stated that 

 he was misled by erroneous information concerning the fos- 

 sils of the loess, for his inclusion of the loess among glacial 

 or subglacial deposits was evidently due largely to this fact. 

 Several species which are not only terrestrial, but frequent 

 uplands, had been reported as aquatic or semi-aquatic; other 



