A CONTRIBUTION TO THE STUDY OF THE SCOTTISH SKULL. 



419 



coefficient of variation 4*74. While the Australian shows the smallest mean value of 

 the three types, it is the most variable. 



With regard to the basion-glabella chord, this in the Tasmanian series varies 

 from 100 to 119 mm., with a mean value of 108'6 mm. The S.D. is 4'84 and V. is 4'45. 

 In the Scottish series the chord varies in length from 98 to 119 mm., with a mean of 

 107'57 mm. The S.D. is 4-183 and V. is 3*88. The mean absolute length of this chord 

 is thus seen to be greater in the Tasmanian series than in the Scottish series, while 

 the variability of the latter is decidedly less than that of the former. In the 

 Australian series the glabella-basion chord varies from 97 to 119 mm., with a mean 

 value of 107 '03 mm., the standard deviation 5 "67, and the coefficient of variation 5*29. 

 The mean value of the chord is thus approximately equal to that of the Scottish 

 series, but the chord in the former is distinctly more variable than the latter. Com- 

 paring the chords as regards their variability, we find the following coefficients of 

 variation : — 



Table XL VIII. 





Glabella-bregma 

 Chord. 



Bregma- lambda 

 Chord. 



Lambda-basion 

 Chord. 



Basion-glabella 

 Chord. 



Tasmanian 

 Australian . 

 Scottish 



V. 556 

 V. 5-08 

 V. 493 



V. 5-27 

 V. 568 

 V. 4-73 



V. 4-0 

 V. 474 

 V. 3-87 



V. 4 45 

 V. 5-29 

 V. 3-88 



In the Tasmanian the variability of the glabella-bregma and bregma-lambda chords 

 is greater than that of the lambda-basion and basion-glabella chords, while the least 

 variable of all is the lambda-basion. In the Australian series of 90 the bregma- 

 lambda chord is most variable, the lambda-basion the least, while the basion-glabella 

 chord is- more variable than the glabella-bregma chord. In the Scottish series we 

 find that, as in the Tasmanian, the glabella-bregma and bregma-lambda chords are 

 decidedly more variable than the lower two, and the least variable, as before, is the 

 lambda-basion, although this is less marked than in the case of the Tasmanian series. 

 The fact that the glabella-basion chord is more variable than the lambda-basion in 

 the Scottish series may at first sight be thought to be due to the variability in the 

 glabella. We find, however, on comparing the basi-nasal length and the basi-glabella 

 length that, in a series like the present one, though the standard deviation of the 

 former is less than that of the latter, the coefficient of variation of the latter is less 

 than that of the former ; and as this quantity is the true measure of variability when 

 the means of two quantities are unequal, we must come to the conclusion that, in 

 this series, the basi-nasal length is more variable than the basi-glabella length. This 

 may be brought forward as an argument against the use of the basi-nasion line, which 

 is the nearest approach that can be obtained in a non-sectionised skull to Huxley's 



basi-cranial axis, as a base line. 



TRANS. ROY. SOC. EDIN., VOL. LI, PART II (NO. 9). 59 



