50 



Proceedings of the Royal Physical Society. 



In comparing the face as a whole with the cranium as a 

 whole, two indices appear to be called for. One, which we 

 may call the upper cranio-fa^ial index, states the length of 

 the roof of the cranium (fronto-parietal length), in terms of 

 the length of the face (taken as 100). The other, the lower 

 cranio-facial index, enables us to state the length of the face 

 as compared to the entire length of the skull. A casual 

 examination of these two indices may lead one to suppose 

 that one or the other is superfluous, and that they will 

 merely state the same fact in different ways. But ex- 

 perience shows that they are both necessary, owing to 

 differences in the conformation of the cranial roof, and 

 varying degrees of backward projection of the occipital 

 region in different skulls. A straight line joining the 

 nasion to the lambda does not always form the same angle 

 with a vertical coronal plane ; nor does a line joining the 

 lambda and the opisthion always meet a horizontal plane 

 at the same inclination. Hence the necessity for the two 

 indices. 



Results. 



I have applied the above method to over fifty skulls of 

 animals belonging to various orders of mammals ; and may 

 illustrate ihe results by arranging the indices of representa- 

 tive animals in a descending order. 



