*gnathic*

a. [ Gr. gna`qos the jaw. ] (Anat.) Of or pertaining to the jaw. [ 1913 Webster ]

Gnathic index, in a skull, the ratio of the distance from the middle of the nasofrontal suture to the basion (taken equal to 100), to the distance from the basion to the middle of the front edge of the upper jaw; -- called also alveolar index. [ 1913 Webster ]

Skulls with the gnathic index below 98 are orthognathous, from 98 to 103 mesognathous, and above 103 are prognathous. Flower. [ 1913 Webster ]