LOO BUREAU OF AMERICAN ETHNOLOGY [BULL. 33 
able number (enumerated on page 96), and the writer will utilize this 
occasion to give a brief description, with illustrations, of the more 
remarkable of these specimens, without attempting to explain the 
exact nature and cause of their peculiar features. 
The whole subject of exceptionally large supraorbital arches and 
low foreheads deserves exhaustive anatomical study. A low sloping 
forehead does not occur or has not yet been observed in the fetus 
and in infants and is extremely rare in the female sex. The same is 
true also of heavy supraorbital ridges. Hence both of these characters 
must be regarded as primarily adult and sexual. Their relation is not 
constant. Most frequently heavy ridges and low forehead coexist 
and accentuate each other, but low front can be found, as will be 
seen in some of the specimens to be described, associated with only 
moderate ridges, and prominent brows are occasionally observed in 
skulls with good frontal arching. The ridges themselves offer sev- 
eral points for study. Ordinarily they form elevations which extend 
over from one-half to two-thirds of the median part of the supra- 
orbital space, but in rare cases they extend along the whole supra- 
orbital border, constituting an uninterrupted arch which may have 
a significance different from that possessed by the ridges of the more 
usual character. They are affected in volume by the frontal sinuses, 
but large ridges may coexist with relatively small sinuses and vice 
yersa, showing that some range of variation is inherent in the bony 
elevations themselves. The corrugator supercilit muscle attached 
to the glabella may also have some influence on the development of 
the parts of the ridges nearest to this attachment. A closer compara- 
tive anatomical study is necessary in this connection. Heavy supra- 
orbital arches and sloping forehead are found in the adult male 
gorilla, but these features are much less apparent in the orang, 
chimpanzee, or gibbon, where we usually find a fairly well arched 
front, as well as in most of the lower primates. 
The following descriptions and measurements of individual skulls 
show that in American crania low forehead and prominent supra- 
orbital ridges are generally not associated with pathological con- 
ditions of the skull, or with premature occlusion of any of the 
sutures; where synostosis was observed, it was plainly senile in 
character. A number of the skulls show small size and according to 
the ordinary classification would be ranged as microcephals, but 
Indian skulls of these dimensions are not rare, and it 1s impos- 
sible to say that the small size of the brain of the individual is 
causally connected with the character of the front of any of the 
specimens. In two of the cases it will be seen that the cranial 
capacity is very fair for Indians. It is an interesting fact that, 
with one not very pronounced exception, all the low-front crania 
in the National Museum collection are dolichocephalic or mesocephalie, 
