History of the United States : From the Earliest Discovery of America to the Present Time, Volume III (Illustrated)

“The numerous varieties of ancient Americans reduce to two distinct types --the Dolicocephalous or long-skulled, and the Brachycephalous or short-skulled. Morton names these types respectively the Toltecan and the American proper. The Toltecan type was represented by the primitive inhabitants of Mexico and by the Mound-builders of our Mississippi Valley; the American proper, by the Indians. The Toltecans made far the closer approach to civilization, though the others possessed a much greater susceptibility therefor than the modern Indians of our prairies would indicate.”