THE EVOLUTION OF THE EYEBROW REGION OF THE FOREHEAD. 291 



Type I. — There are many human crania in many different races in which the three 

 elements of the supraorbital region are distinct and separate. The same also may be 

 observed in certain species of ape. 



The supraorbital margin extends in a continuous and arch-like manner from the 

 fronto-malar suture on the outer side to the fronto-maxillary suture on the inner side. 

 It is divided into a long outer part and a shorter inner portion by the supraorbital 

 notch. The outer portion is a projecting and sharply defined edge ; the inner part, 

 quite distinct from the superciliary arch, sweeps downwards immediately in front of 

 the trochlear pit, and although much less prominent than the outer part is yet quite 

 obvious (fig. 4). 



The superciliary ridge or arcus superciliaris is a semilunar, smooth elevation which 

 lies above the inner part of the inner portion of the supraorbital margin (fig. 4). Its 

 inner end curves downwards into the glabella, and is separated from the corresponding 

 eminence of the opposite side by a narrow, shallow median depression ; its outer end 

 fades away as it approaches the trigonum supraorbitale. 



The trigonum supraorbitale lies to the outer side of the superciliary eminence. It 

 is a triangular depressed field, with its apex at the fronto-malar suture, which is included 

 between the outer part of the margo supraorbitalis and the anterior prominent part of 

 the temporal ridge. 



Fig. 4 is taken from a lecture specimen of the frontal bone which I am in the 

 habit of using for class purposes. Fig. 5 is the frontal bone of a Kham warrior from 

 Thibet, in which Type I. of the supraorbital region is particularly well marked. Owing 

 to the somewhat unusual length and strongly curved character of the superciliary 

 arches, the supraorbital region in this skull presents a striking appearance. The 

 trigonum supraorbitale is very depressed. 



This type of eyebrow region does not appear to be distinctive of, nor indeed more 

 frequently present in, any one race more than another. It occurs in most, if not in 

 all, recent races, and even amongst Australian skulls it is not infrequently met with, 

 as will be seen from the following figures : — 



Number of Times present in a Group of 25 Australian Skulls. 



Natives of Victoria — 8 males . . . 1 • 



5 females . . 2 



Natives of Queensland — 10 males ... 1 



2 females . . 



In this small group of Australian skulls, therefore, Type I. of the eyebrow region 



occurred four times, or in 16 per cent, of the specimens. 



This type of the supraorbital region is also seen in certain apes, although probably 



in no case is it to be regarded as distinctive of any particular species. Still, it should 



be noted that it was present in a very definite manner in each of the three specimens of 



Macacus cy clops which I had the opportunity of studying. 



TRANS. ROY. SOC. EDIN., VOL. XLVI. PART II. (NO. 12). 44 



