148 A. W. Tucker and C. S. Myers.—A Contribution

especially when we find the nasal indices of the Nubawi and Furawi, who live in the same region as the Tagalawi, to be 101T8 and 102*63 respectively. Next to the Shilluks come their neighbours the Dinkas with a nasal index of 98*99. These indices differ by 5*67, but the probable error of this difference reaches + 2*30, a value relatively far too high for the difference to be with any probability significant.

The rest of the eastern Sudanese are far more platyrhine than either the Dinkas or the Shilluks. The index of the Nubawi exceeds that of the Shilluks by

7*86 while the probable error of the difference between the two means is only + 2*02, so that the difference is with some probability significant. On the other hand, in the case of the Nubawi and Furawi these means differ only by 1*45, while the probable error is actually greater than this, + 1*5. If we compare these results with those obtained for the cephalic index, we find a correlation between less marked dolichocephaly and very marked platyrhiny and between more marked dolichocephaly and less marked platyrhiny.

Upper Facial Index.—This shows no great variation among the different tribes. The lowest is that of the Tagalawi, 44*41; while the highest is that of the Shilluk, 47*12. The values of the upper facial index seem to vary inversely with those of the cephalic and with those of the nasal index, a lower facial index going with a higher cephalic and nasal index, and a higher facial index with a lower cephalic and nasal index. At the one extreme we have the dolichocephalic, less platyrhine, leptoprosopic Shilluk ; at the other the mesaticephalic, more platyrhiny chamaeprosopic Tagalawi.

Radio-gnathic Index.—This index expresses the relation between the auriculo- alveolar radius and the auriculo-nasal radius, a not very satisfactory measure¬ ment.1

It is curious to find that the Shilluks and the Dinkas, though having narrower noses and longer faces than the Furawi and the Nubawi, are not less but perhaps more prognathous. In Table I the Bertawi have the lowest index, 107*03, while in Table II the Hamagawi, of which tribe the Bertawi are thought to be a branch, have an index as low as 103*91, which value is actually reached by the natives of Upper Egypt.2 From our study of the cephalic, nasal, upper facial, and gnathic indices it seems probable that the tribes living on the banks of the Nile and its tributaries (<e.g., the Shilluks and the Dinkas) are more dolichocephalic, less platyrhine, more leptoprosopic, and perhaps more prognathous, than the south¬ western Bahr el Ghazal tribes (Bongawi, Fertitawi, Niam-niam), the tribes of Dar Fur and Dar Nuba, or those of the Blue Nile.

Stature.—In the following table the average stature of the chief tribes is given, with the number measured in each tribe :—

1 To make the index significant it is necessary to know the size of the angle enclosed by the two linear measurements on which the index is based. See Man, vol. iii, 1903-4,, pp. 12, 13.

2 Cf. Journ. Ry. Anth. I?ist., 1906, vol. xxxvi, p. 239.