Lansing Pleistocene Geology. — Winchell. 291 
APPENDIX A. 
The following letters throw additional light on the question of the 
age and nature of the deposit in question. It is evident that the ter- 
races of the Missouri should have special examination. 
Note from Professor IVilliston. 
Chicago, Feb. 17, 1903. 
Dear Professor WincJicll: Pardon me for not replying immedi- 
ately to your letter. 
The clam was dug from the extreme angle of the tunnel, near the 
door, by Mr. Long and myself, at about seven feet above the floor, that 
is where the roof joins the wall. We at first thought it was bone, and 
I did not recognize that it was a cast until after I examined it at 
Lawrence. The hinge line and markings of both lateral valves were 
(and are, if they have not since been injured) quite complete. There 
is no doubt but that it is a river clam, though I did not attempt to 
identify the species. Why it should have lost its structure and have 
been replaced by a cast I do not know. The specimen is now at the 
University of Kansas, with other shells from the walls. 
Sincerely yours, 
S. W. WiLLISTOX. 
Criticism by Professor Todd. 
Prof. N. H. Winchell, 
Dear Sir: I thank you for the courtesy shown me in askmg that 
I should criticise in any waj* your able paper in reply to professor 
Chamberlin. I regret that it has come to hand when I have not had 
time to do the subject justice and yet return it in reasonable time for 
publication. I can only briefly express some of the opinions I hold on 
the various questions raised, without presenting very clearly my rea- 
sons for the same. 
The frequent gradation of the till into stratified drift and that in 
turn into loess, both laterallj' and vertically, I concede cheerfully, but 
loess, so far as I have observed, very rarely contains pebbles or er- 
ratic particles larger than half a millimeter in diameter. Particularly 
is this true remote from glacial moraines. Moreover, mere composi- 
tion and physical properties, such as unstratified character, presence 
of concretions and vertical cleavage, do not clearly distinguish it from 
quite recent flood deposits. The latter are more likely to have er- 
ratics of some size scattered through them. 
I. The point in your paper which strikes me with the strongest 
novelt}', is your conclusion that the terraces of the early Wisconsin 
stage would pass below the present level of the Missouri above Lans- 
ing. Since Mr. Upham has arrived at the same conclusion I must 
believe there must be some reason for the view, though I cannot see 
it. I know of no other evidence of a crustal change which that would 
involve, no overlapping deposits, changes of drainage or warping of 
upland levels. 
