In Africa, it is the low Alluvia of rivers that favour the Negro configuration.
"The Ethnology of the British Colonies and Dependencies"
Robert Gordon Latham
These subterranean vaults are usually filled in part with mud, pebbles, and breccia, in which bones occur belonging to the same assemblage of animals as those characterising the Post-pliocene Alluvia above described.
"The Student's Elements of Geology"
Sir Charles Lyell