GORILLAS— PITMAN 255 



readily recognizable owing to tlie freedom from appreciable spacing 

 between the teeth. This spacing is a result in infancy of food pack- 

 ing, tough fibrous pieces of the bamboo shoots becoming wedged be- 

 tween the teeth and gradually pushing them apart. In due course, 

 this has developed the spacing as a constant, and possibly now in- 

 herited feature. 



This difference, slight though appreciable, is scarcely a basis for 

 satisfactory separation but it does indicate that the mountain gorillas 

 respectively in the widely different, florally and climatically, regions 

 (a) west of Lake Kivu, (&) southwest (or westerly) of Lake Edward, 

 (c) the Birunga Mountains, and (d) the Kayonsa may to a certain 

 extent differ from each other. The representatives from west of 

 Lake Edward have been separated from heringei under the attractive 

 and descriptive title of rex-pygmaeorum,^ though the material on 

 which the separation is claimed is scanty. With adequate compara- 

 tive material it might be possible to separate racially the typical 

 mountain gorilla of the excessively humid bamboo and hagenia- 

 covered mountain slopes of the elevated Birunga Mountains from 

 those of the drier localities from which the bamboo is absent. If such 

 is the case, then the Kayonsa representative will possibly be found to 

 be an extreme form of the latter as a result to a certain degree of 

 environment, but particularly owing to a general absence of the juicy 

 vegetable food of which the gorilla is so fond. 



There unfortunately being no material available for scientific 

 study, with the exception of an old skull from this region, and little 

 likelihood of any being procured at any rate in the near future, the 

 status of what may prove to be a specialized race has to be based 

 mainly on assumption. 



Ecological facts which are definitely known, and which show great 

 divergence from the Birunga zone, are : 



(1) There is in the Kayonsa a complete absence of bamboo, wild 

 celery, dock, and similar juicy-stemmed plants such as abound in the 

 humid, high altitudes, forcing the gorilla to confine its diet to a 

 mixture of leaves, berries, ferns, the tender fronds of tree-ferns, parts 

 of the wild banana stems, and leaves, and fibrous bark peeled off a 

 variety of shrubs in the undergrowth. Examples of some of these 

 botanical specimens submitted to the British Museum (Natural His- 

 tory) for expert determination which have been identified include 



* The name of the Kayonsa gorilla. — Captain Pitman has kindly sent some skulls of the 

 Kayonsa gorilla to the British Museum (Natural History), where I have been able to 

 examine them. In the shape of their nasals, the possession of a distinct masseteric knob 

 on the zygoma, and the position of their incisive teeth, they perfectly agree with the 

 gorilla from the Birunga volcanoes, and can easily be distinguished from the races living 

 west of the central African Rift, G. g. graueri Matschie from the isolated forest at Siba- 

 toa's, northwest of Lake Tanganyika, and ff. g. rex-pygmaeorum Schwarz from the east- 

 central forest. — Ernst Schwabz. 



