These ridges, as is well known, are sexual characteristics in the main;
phylogenetically they are the remains of the pronounced supraorbital
arches of man’s anthropoid ancestors and of early man. Like the
mastoids they show also considerable individual variation in each sex
among the Indians, owing to which they occasionally fail to afford aid
in the determination of the sex of the specimen. As a rule they are
limited in Indians to the median half to two-thirds of the supraorbital
space. In the Munsee skulls at hand they are markedly developed in only
one of the males; in two of the male skulls they are small, feminine
like, while in two of the female skulls they are so developed as to
approximate the supraorbital ridges of the average male.
[Illustration: BUREAU OF AMERICAN ETHNOLOGY BULLETIN 62 PLATE 14