XLII \UIIj luti'mlm-litm w\\\ 



TAHLK XLII. 



Tin; (h-cifiitnl li.ili-x (Oc. I) determined front the Occipital Arc (<Sj) and the 

 Occipital Chord (6V). (Biometrika, Vol. xin. p. 2(Jl, M. L. Tildi-sl?y.) 



The Occipital Index is a measure of the < -rcln-llar development in individual 

 or race. The arc $3 is measure<l on the ukull from lambda to opisthion with the 

 tape, and the chord between the same two points with the callipers. The formula 

 for the Occipital Index is 



IQOfl* 



The Oc. 7 is tabled for R= S 3 /S 9 ' from 1O50 to I'oOO. For craniometric purposes 

 it is rarely needful to interpolate into the Table. 



Illustration. For two crania we have respectively 



#3 = 114-7, 5,' = 98-6, and S 3 = 110-0, ,' = 95-4. 

 Hence: S S /S 3 '= 1163 for the first, and = M53 for the second. 



Accordingly the occipital indices by the Table are 63*41 and 64'61 ; the occipital 

 is thus flatter in the second than in the first skull. They correspond to the mean 

 crania of men and women of the same race. 



TABLE XLIII. 



Coefficients for Sfieppard's Quadrature Formula (c). (Biometrika, Vol. I. p. 276, 

 and P. F. Everitt, ibid. Vol. xn. pp. 282283.) 



This particular quadrature formula has been found very satisfactory in a number 

 of cases, where the curve represents a continuous mathematical function. The 

 formula supposes the area to be divided into p trapezettes on bases of equal size- //. 

 Then A , the chordal area, is given by 



where z , Zi, z^, ... Zp-i, z p are the p + 1 equally spaced ordinates forming the sides 

 of the trapezettes. The required area of the curve is then 



Area = A c + d {(zj - *) - (^ - *p-i)} h 



h 

 A. 



Here Ci, C t , C a are certain functions of p provided in Table XLIII. They are se- 

 lected to give the best result, provided we stop at third terminal differences. 



