THE DEVELOPMENT OE SKULL AND BRAINS. 657 



''Trinir' skullcaps. According to some authorities, both these skull- 

 caps are undouV)tedly human, while others hold that the " Neandei-thal '' 

 belongs to an extinct species of the genus Homo, and the "Trinir" is 

 the remains of an extinct genus — P/tJiecanthi'opus erectun of Dubois — 

 intermediate ))etween luan and the anthropoids. One of the most 

 obvious and easily recognized peculiarities of these skullcaps is the 

 very marked prominence of the supraor})ital arches. The ghibella- 

 occipital length of the Neanderthal is Sd-t millimeters, and the greatest 

 transverse diameter, which is over the parietal region, is 1.52 milli- 

 meters^ — an index of 74.51 — while the much smaller Trinil calvaria, with 

 a length of 181 millimeters and a breadth of 130 milimeters, has an index 

 of 71.8. Both of these skulls are therefore slightly dolichocephalic. 

 Schwalbe has corrected these figures by making reductions in their 

 lengths on account of the frontal "outworks,'" so that he estimates the 

 true length-])readth index of the Neanderthal as 80 and that of the 

 Trinil as 75.5. These indices, thus raised about 5 per cent, are con- 

 sidered to represent approximatel\' the length-breadth index of the 

 cranial cavity. A comparison of the external and internal measure- 

 ments of many recent skulls with prominent glabelhe would, I suspect, 

 show a greater difl'erence than that calculated by Schwalbe for the 

 Neanderthal and Trinil specimens. In a male skull, probably an 

 aboriginal Australian, with a cranial capacity of 1,227 cubic centi- 

 meters, I found that the glabella-occipital length was 189 millimeters 

 and the transverse diameter at the parieto-squamous suture 127 milli- 

 meters, which gives an index of 67.20 and makes the skull decidedly 

 dolichocephalic. The length of the cranial cavity, however, was 157 

 millimeters and the breadth 121 millimeters (an index of 77.07 and a 

 difference of nearly 10 per cent), so that while from external measure- 

 ments the skull is distinctly dolichocephalic, the proportions of its cavity 

 are such that it is mesaticephalic. It is probable that many skulls 

 owe their dolichocephalic reputation simply to the prominence of the 

 glabella and supraorbital ridges. An excessive development of these 

 structures is also liable to give the erroneous impression of a retreat- 

 ing forehead. In tlie Australian skull just mentioned the thickness of. 

 the cranial wall at the glabella was 22 millimeters. From this level 

 upward it gradualh' thinned, until 45 millimeters above the glabella 

 it was only millimeters thick. When the bisected skull was placed 

 in the horizontal position the anterior surface of the frontal bone 

 sloped from the glabella upward and distinctly })ackward, while the 

 posterior or cerebral surface was inclined upward and forward. In 

 fact, the cranial cavity in this region was separated from the lower 

 part of the forehead by a wedge-shaped area having its apex upward 

 and its base below at the glabella. 



The cranial wall opposite the glabella is not appreciably thicker in 

 the Neanderthal calvaria than in the Australian skull to which 1 ha\ c 



