NOTES ON THE GORILLA 629 
Zygomatie width — Coast greater, Mountain lesser. 
Mastoid width — Coast greater, Mountain lesser. 
External cranial width — Coast greater, Mountain lesser. 
Orbital width — Coast greater, Mountain lesser. 
Outside intercoronoid width — Coast greater, Mountain lesser. 
In all the above, the Coast is the greater, except in length of palate. 
The following measurements show the same grouping to a smaller but never- 
theless noticeable degree. 
Basion-nasion — Coast longer, Mountain shorter. 
Cranial height — Coast greater, Mountain lesser. 
Condylar width — Coast greater, Mountain lesser. 
The following tend to group the Mountain gorillas together with usually 
one group of the Coast gorillas as a sort of intermediate between the Mountain 
and the other Coast animals. 
Basal length — Mountain greater, Cameroons intermediate, Coast lesser. 
Cranial length — Coast greater, Western Cameroons intermediate, Mountain lesser. 
Orbital are (average) — Coast greater, Western Cameroons intermediate, Mountain lesser. 
Greatest width across jaws posteriorly — Mountain greater, Western Cameroons intermediate, 
Coast lesser. 
It seems as if there were sufficient difference of degree with intergradation 
to indicate subspecific relationship between the Mountain and the Coast gorillas. 
The following tooth measurements show such uniformity that of themselves 
they can justify no subdivision of the species. 
Length of upper tooth row c-m? 
Length of lower tooth row c-ms 
Outside alveolar width across m? 
Outside alveolar width across m? 
Inside alveolar width across m? 
Inside alveolar width across me 
The following characters show such an enormous individual variation that 
they are of no value in subdividing the species: — 
Sagittal are. 
Height of occiput. 
The following measurements show uniformity, except with respect to one 
group, that may make them of interest : — 
Height of ascending process of ramus, uniform (except in a small group of Western Cameroons 
gorilla). 
Greatest anteroposterior length of ascending process of the ramus, uniform (exception, 
Kivu ramus slightly narrower than rest). 
Outside intercondylar width, uniform (exception, Eastern Mountain the narrowest). 
Having tabulated measurements that show no difference in degree and those 
that divide the skulls into two groups, we may now consider the geographical 
groups, one by one, and any significant characteristics that are revealed in their 
curves or measurements. 
