422 DR MATTHEW YOUNG. 



chord varies in length from 46 mm. to 88 mm., with a mean length of 65"19 mm.; 

 the S.D. is 7730 and V. equals 11 '85. This chord is, to a certain extent, a measure- 

 ment of the length of the corresponding arc, and illustrates its variability. 



In the Australian skull figured by Klaatsch the length of the chord is 64 mm., 

 which is approximately equal to the mean length in the Scottish series ; but in the 

 Australian series of 90 the chord shows a range of variation from 41 to 69 mm., with 

 a mean value of 52*43 mm., which is slightly less than the mean value of the Tasmanian 

 and more than 13 units less than the Scottish mean value. As the standard deviation 

 is 5"65, and the coefficient of variation 1077, the chord is not so variable in the 

 Australian as in the Tasmanian and Scottish series. 



The inion-basion length varies in the Tasmanian series from 77 to 96 mm., 

 with a mean of 86 mm. ; in the Scottish series from 68 to 97 mm., with a mean of 

 86'44 mm. ; in the series of 90 Australian skulls from 68 to 101 mm., with a mean 

 value of 8 6 '48 mm. The mean is thus practically equal in the three series. 



In the Tasmanian the basion-prosthion chord varies from 88 to 111 mm., with a 

 mean of 99'6 mm. ; in the Scottish series the chord varies from 81 to 107 mm., with 

 a mean of 94'87 mm. The mean value of this chord is thus considerably less in the 

 Scottish skulls than in the Tasmanian, while the value of this measurement in 90 

 Australian skulls ranged from 84 to 120 mm., with a mean value of 99'86 mm., i.e. 

 practically equal to that of the Tasmanian. 



The prosthion-glabella length in the Tasmanian series varies from 62 to 88 mm., 

 with a mean value of 73'5 ; in the Scottish series the length varies from 71 to 93 mm., 

 with a mean value of 80'87 mm. The mean length in the Scottish skull is thus con- 

 siderably greater than in the Tasmanian, while the mean length of 90 Australian 

 specimens was 7472 mm., just a little greater than the value in the Tasmanian. 



With regard to the respective heights of the frontal, parietal, and occipital 

 arcs, the following values have been obtained in the present Scottish series : — The 

 frontal varies from 15 to 30 mm., with a mean height of 21 '69 mm.; the parietal 

 varies from 16 to 30 mm., with a mean height of 23 "49 mm. ; and the occipital 

 varies from 3 to 19 mm., with a mean height of 9 '7 6 mm. Of these heights the 

 occipital is much the most variable, and the frontal is slightly more variable than 

 the parietal, as will be seen by comparing their coefficients of variation in the table 

 that follows. 



Measurements for the above dimensions are given for the Tasmanian series of 

 skulls, 50 in number, in Buchner's paper (61) "On Curvatures of the Tasmanian 

 Aboriginal Crania." The frontal arc height varies from 10 to 25 mm., with a mean 

 value of 18 '9 mm. ; the parietal arc height from 19 to 28 mm., with a mean value 

 of 23"3 mm. ; and the occipital arc height from 2 to 12 mm., with a mean value 

 of 6*1 mm. 



Turner (47) gives values for the heights of the bregma-glabella arc perpendicular 

 in series of Tasmanian, Scottish, and Australian skulls. In 7 Tasmanian the per- 



