These are represented quite poorly. In almost half the skulls there are
no parietal foramina at all, while in most of the remainder they range
from very minute to medium size, of which latter there is a single
instance, and in only one case are there two canals of medium size.
The exact significance of this showing is not clearly understood. When
present these canals transmit, as is well known, a small arteriole and
an emissary vein which connects the venous systems within and without
the wall of the skull.
[Illustration: BUREAU OF AMERICAN ETHNOLOGY BULLETIN 62 PLATE 13