630 REPORT OF THE HARVARD AFRICAN EXPEDITION 
Under Mountain Gorilla: — 
Kivu: Height of occiput — shortest. 
Greatest anteroposterior length of ascending ramus — least. 
Outside alveolar width at m?— least. 
Length of upper tooth row, c-m’ — longest. 
Sagittal are — least (lowest crest). 
Length of rostrum — shortest. 
Eastern Mountain: Outside intercondylar width — least. 
Under Coast Gorilla: — 
Cameroons: None. 
Gaboon: Cranial length — longest. 
Orbital are — greatest. 
Western Cameroons: Palatal length — shortest. 
Orbital width — greatest. 
Cranial length (divided into two groups, one similar to Mountain, other to Coast). 
Intercoronoid width — greatest. 
Height of ascending process of ramus — small group from this region have much the 
shortest. 
Under this grouping the Kivu and the Western Cameroons would be the only 
groups worth considering as possibly separable from the rest. The distinctive 
differences are all small and do not seem to be of sufficient degree to justify 
making either of these groups a separate subspecies in the present state of our 
knowledge. 
Briefly to sum up: — The African gorillas show no differences of kind suffi- 
cient to justify the recognition of more than the one original species Gorilla gorilla 
(Savage and Wyman). There does exist, however, a difference in degree not very 
great, but sufficient to separate the Coast from the Mountain gorillas. These 
differences based on average skull measurements give the Coast gorilla the maxi- 
mum in greatest total length, zygomatic width, mastoid width, external cranial 
width, orbital width, outside intercoronoid width, basion-nasion, cranial height, 
and condylar width; the Mountain gorilla the maximum in palatal length. 
As the type form is the Coast gorilla and the first-described Mountain gorilla 
was Gorilla gorilla beringer, it is proper to use the latter name for our Mountain 
gorilla subspecies. Undoubtedly some naturalists will distinguish the Eastern 
Mountain race from the Kivu and will continue to use for it the name graueri, 
and for the Coast gorilla of the Western Cameroons the name diehli. However, 
from a study of the existing specimens of gorillas in the museums of the world, 
I see no sufficient justification for giving graueri or diehli the rank of a distinct 
subspecies. 
There exists then only one species represented by two forms: — Gorilla gorilla 
gorilla from the coast and Gorilla gorilla beringei found in the mountains of the 
eastern Congo. 
The conclusion says with regard to classification: 
In this study I have tried to bring out what seem to me the important specific 
or subspecific differences found among gorilla skulls in view of the new light and 
knowledge that we have on the matter of individual variation. 
