628 REPORT OF THE HARVARD AFRICAN EXPEDITION 
It was in collecting this specimen that I first became interested in the study 
of gorillas, and was surprised to find how comparatively little scientific knowledge 
there was about this animal. A year’s research work in zoology in Cambridge, 
England, gave me an opportunity to study the gorilla, to visit the important 
museums where there are large collections of skulls, and to gather the necessary 
material for the publication of the revision and classification of the group. 
Since a dozen or more different species of gorilla are currently recognized in 
nomenclature, a special study was made in order to see which of these might be 
valid. In the course of this investigation most of the material in the larger 
museums of Europe and America has been carefully studied, measured, and 
photographed, and the types of practically all the named races were seen. By 
way of summary, it may be said that most of the nominal species that have been 
described in the last thirty years are based on extremes of variation and do not 
represent distinct geographical forms. The existing races of Gorilla are here 
recognized as: the Coast gorilla (Gorilla gorilla gorilla of Savage and Wyman), 
found in the lowlands of the Cameroon and Gaboon region; and (2) the Mountain 
gorilla (Gorilla gorilla beringei of Matschie), which occurs in the forests of the 
Kivu country and the mountainous regions of Central Africa immediately west 
of the Great Lakes. The characters separating these two forms are set forth in 
detail in the complete report. Their ranges are apparently distinct, for there is a 
considerable intervening area in the northern Congo region over which gorillas 
are not known to occur. 
In the complete monograph ! the summary of the comparison of skulls says: 
In all the twenty-six measurements just recorded there is such uniformity that 
there are no grounds for doubting that all the gorillas measured belong to one 
species. The tooth measurements are remarkably similar and suggest no basis 
for subdivision of the species. The length and width of the ascending branch of 
the ramus, the length of the occiput, the height of the sagittal crest, all show con- 
siderable variation that is very much an individual characteristic, but in no way 
correlates the skulls into definite groups. 
When dealing with the most important measurements, while there is no 
doubt that all the gorillas belong to a single species, one does find a certain group- 
ing of the skulls within this species. The curves that represent these more im- 
portant measurements all overlap each other, which shows an intergradation, 
but the peaks of the curves do not necessarily coincide. They show a distinct 
division into two groups: the Kivu and Eastern Mountain making up one 
group, and the Cameroons, Gaboon, and Western Cameroons representing the 
other group. 
By way of summary, the following important measurements indicate a divi- 
sion into two groups, the Coast and the Mountain gorillas. These measurements 
overlap, but nevertheless show a significant difference in their averages. 
The greatest total length — Coast longer, Mountain shorter. 
Palatal length — Coast shorter, Mountain longer. 
1 Coolidge, Harold J., Jr.: ‘A revision of the genus Gorilla.” Mem. Mus. Comp. Zoology at Harvard 
College, vol. 50, No. 4, August 1929, pp. 293-381, 21 Plates and 2 Maps. 
