
616 The American Naturalist. [July, 
Prof. Osborn in his review alludes to “ the extremely complex 
and confusing dentition” of some Mesozoic mammals, and of the 
truth of this statement his own papers afford many illustrations 
besides those here mentioned. What this perplexing subject 
really needs, however, is more facts and less theories. Believing 
this, I have endeavored to secure new facts by long and laborious 
explorations, hoping in this way to clear up some of the confu- 
sion which so puzzles fireside naturalists. The 1,500 specimens 
Mesozoic mammals I have thus secured, fragmentary though most 
of them are, will, I trust, prove of some service in this work, 
although their full investigation has been delayed by other 
duties. 
No one who has earnest work to do can afford to spend time 
in the ungracious task of pointing out errors in the work of 
others. For this reason, I have hitherto said nothing about the 
mistakes in Prof. Osborn’s papers on Mesozoic mammals, intend- 
ing to wait until my own memoir on the subject, for which I have 
collected so much material, should make it my duty to review the 
whole subject. The injustice of his criticism on my preliminary 
work while in progress made a brief reply necessary. The full 
discussion, I must still reserve for my memoir. 
New Haven, Conn., April roth, 1891. 

