304 The American Naturalist. [April, 
pendent of any active current or other displacing powers; 
and lastly, because there is no mixture of diluvial drift with 
the blue clay, which latter retains its homogenous character 
equally in the higher parts which furnished the extinct quad- 
rupeds and in its lower part which contained the remains of 
man.” These specimens thus found associated were made the 
subject of investigation by Sir Charles Lyell, and afterwards 
by Dr. Joseph Leidy, the latter having published a memoir 
with illustrations of the human bone in the Transactions of 
the Wagner Free Institute of Science, vol. ii, p. 9. He says, 
“It differs in no respects from an ordinary average specimen 
of the corresponding recent bone of man.” 
Dr. Leidy says Lyell expressed the opinion that, although 
the human bones may have been contemporaneous with those 
of the extinct animals with which it has been found, he 
thought it more probable that it had fallen from one of the In- 
dian graves and had become mingled with the older fossils 
which were dislodged from the deeper part of 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, subse- 
quently on the latter.” 
Although Dr. Leidy testifies to the general similarity of ap- 
pearance of the human with the other bones, it does not séem 
to have occurred to him to have them analyzed and compared. 
Remembering the story told by the analysis and consequent 
comparison of the Calaveras skull with that of the rhinoceros 
teeth found in a formation corresponding in age, though in a 
different locality ; and of the fact apparent therefrom that the 
Calaveras skull was in an equally advanced stage of fossiliza- 
tion as the rhinoceros teeth, I deemed it wise to make an ex- 
amination and test by analysis. To this end I applied to 
Prof. Angelo Heilprin, and through him to the authorities of 
the Philadelphia Academy of Natural Sciences, 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 thé mylodon, choosing those which, for size, 
texture and general appearance, bore the greatest likeness one 
