630 The American Naturalist. [July, 
the cliff, and Dr. Leidy adds: “In the wear of the cliff the upper 
portion, with the Indian graves and human bones, would be likely to 
fall first, and the deeper portions with the older fossils, subsequently on 
the latter.” 
Although Dr. Leidy testifies to the general similarity of appearance 
of the human with the other bones, it does not seem to have occurred to 
him to have them analyzed and compared. Remembering the story told 
by the analysis and consequent comparison of the Caleveras skull with 
that of the rhinoceros skull found in a formation corresponding in age, 
though in a different locality ; and of the fact apparent therefrom that 
the Caleveras skull was in an equally advanced stage of fossilization 
as the rhinoceros skull, I deemed it wise to make an examination and 
test by analysis. To this end I applied to Prof. Angelo Heilprin, and 
through him to the authorities of the Philadelphia Academy, so a few 
months since specimens certified by Prof. Heilprin have been taken, 
one from the bone of the man and the other from one of the bones of 
the mylodon, choosing those which for size, texture and general appear- 
ance bore the greatest likeness one to the other. These were submitted 
by me to Prof. F. W. Clarke, Chemist of the United States Geological 
Survey, on duty at the National Museum, who has just returned the 
result of his analysis, which is here published for the first time. 
Two Foss. Bones. 
Man. Mylodon. 
Per cent. Per cent. 
‘Loss at 100°C Aonar? EO 6.77 
Loss on ignition 16.54 21.18 
Silica OJ... 22.59 3.71 
Phosphoric acid P Oa 17.39 23.24 
Alumina........... (AL 0J.: 3.21 4.02 
Tron: protoxides..0..c080 00.8085: (Fe O)...... 5.65 4,44 
Maganese protoxide................. (Mn O)...... 1.65 3.40 
Lime (Ca O)...... 25.88 30.48 
Magiida 005. cide, (Mg 0)...... 0.95 0.78 
98.41 97.02 
Alkalies, carbonic acid and fluorine were not looked for, owing to- 
small amount of available material, hence the low summation. 
The importance of this analysis will be apparent at a glance. The 
human bone is in a higher state of fossilization than is that of the 
