calaveras skull

from The Century Dictionary.

• noun See skull.

from the GNU version of the Collaborative International Dictionary of English.

• A human skull reported, by Prof. J. D. Whitney, as found in 1886 in a Tertiary auriferous gravel deposit, lying below a bed of black lava, in Calaveras County, California. It is regarded as very doubtful whether the skull really belonged to the deposit in which it was found. If it did, it indicates an unprecedented antiquity for human beings of an advanced type.