Width of the ocular rima: between the two extremities of the rima.
Width of the labial rima: between the two extremities of the rima.
Length of the ear: from the highest upper edge of the auricle to the lower extremity of the lobule.
Index of the ear: this is obtained, by the well-known formula, from the length and breadth. The normal index is 50; the types of ear above 50 are low types.
Anthropologists obtain the facial index from the skeleton, especially for the purpose of determining the proportion of the face in human remains found in the geological strata. In such crania the mandible is wanting, and the teeth are wanting. Consequently, there are several ways of computing the facial index, because, while the transverse or bizygomatic diameter, which is considered as the lesser diameter, always remains constant, the longitudinal, which is considered as the greater, varies. The longitudinal diameter is calculated sometimes from the ophryon to the chin, at others from the ophryon to the point of insertion of the two upper middle incisors. In the first case it is now less, and again greater than the bizygomatic diameter; in the second case, it is always less, and the resulting facial index is notably greater than 100.
The most usual formula for the facial index is the following:
Fi = (bizygomatic diameter×100)/(ophryo-mental diameter)
on the basis of which Pruner Bey gives the following mean averages according to race, for the general facial index:
| Arabs | 96.7 |
| Chinese | 101.7 |
| Hottentots | 105.7 |
| Tasmanians | 109.9 |
| Laplanders | 124.7 |