362 SCIENCE PROGRESS. 



yet it has a much more massive development. Unfortun- 

 ately, in the Bengawan and Neanderthal skulls the mastoid 

 region is wanting ; but the arrangement of the occipital 

 crests in these skulls indicates for us that the heads were 

 poised upon the trunk, so that the mastoids must have 

 been approximately similar to those of modern men. The 

 mastoids of the Spy crania measure from the tip to the 

 meatus roof about 26 m.m. ; in the Cynocephalic Australian 

 skulls the measurements vary from 20 to 30 m.m.; while 

 those of modern European skulls are frequently more than 

 30 m.m. In both human and simian babies the mastoid 

 process is absent ; in the first, with years, it grows down- 

 wards to o-ive its muscles leverage for o-entle nodding and 

 turning movements ; in the second, it grows outwards to 

 form the lateral parts of the occipital plateau, and thus 

 enlarge the surface for fixation of the nuchal muscles. This 

 latter also is probably the primitive form, but we cannot 

 say that the fossil human skulls show any approach thereto. 



8. CHARACTERISTICS OF THE CRANIAL VAULTS OF 

 HUMAN FOSSIL SKULLS. 



The Cynocephalic aspect — the retreating forehead and 

 depressed crown — of the Bengawan, Neanderthal, Spy and 

 some Australian crania is due to the absence of the frontal 

 and parietal flexures of the vault. In most modern crania 

 the frontal is bent so that part of it looks forward and gives 

 a basis to the brow, while the other part enters into the 

 formation of the cranial roof. The parietal is also bent, so 

 that anteriorly it forms part of the roof, posteriorly rather a 

 part of the posterior cranial wall. Why the cranial vault 

 should be Hexed abruptly in most modern, and gradually in 

 most fossil, crania is not known, but there can be no doubt 

 that in this respect the fossil crania make a nearer approach 

 to the primitive type and simian form than do modern 

 skulls. 



In the Bengawan skull an obtuse ridge runs along the 

 position of the median frontal suture and the anterior part 

 of the sagittal suture. It frequently occurs in human crania 



