342 NATURAL HISTORY BULLETIN. 



the base of the loess sometimes (though rarely) contain fos- 

 sils is not inconsistent with the seolian hypothesis. The 

 writer has found living Succiiiea grosveuorii in mingled sand 

 aud loess on top of the high ridge northwest of Hamburg, 

 Iowa. Some of the dead shells, still somewhat fresh, were 

 already partly covered with dust and sand. . Some of the sand 

 so transported by wind today is coarse and even contains 

 small pebbles. 



The "southern loess" discussed by McGee, whom Dr. Win- 

 chell quotes so extensively, is the loess of the Iowan border in 

 Iowa, and this rests upon morainic sands,* which must have 

 presented ideal conditions for such a mingling of sand and dust. 

 It is here that his hybrid "drift-loess" was formed. There is 

 no connection, so far as known, between this "drift-loess" 

 and Calvin's "flooded-valley deposits" which are referred to 

 the "drift-loess" by Winchell.f 



The occurrence of real till in loess, excepting where slip- 

 ping may account for its presence, has not yet been demon- 

 strated. Even Bain's example, % is not conclusive. He says 

 that the exposure of till to which he refers is "about 150 feet 

 above the river, and the till is above any similar deposit 

 known to occur in this vicinity." Anyone who is familiar 

 with the topography and altitudes of the part of Woodbury 

 county referred to, will be, very slow to make unquestioned 

 application of Bain's careful statement concerning a point 

 only 150 feet above the river. In any case the extreme rarity 

 of such cases should lead to great caution. Loess and drift 

 are not so intermingled as to warrant sweeping conclusions 

 concerning genetic relationship. 



The fineness and homogeneity of the loess, together with 

 the presence of numerous terrestrial fossils which required 

 abundant vegetation for their maintenance, are sufficient to 



"Calvin, S., la. Geol. Sur., vol. vii, pp. 88-9, 1897. Beyer, S. W., 

 la. Geol. Sur., vol. vii, p. 236, 1897; vol. x, p. 281, 1900. 

 tAm. Geol., 1. c. p. 279. 

 X Cited by Winchell, Am. Geol., 1. c. p. 281. 



