ANATOMY OF THE ANTHROPOID APES. 183 



species : ia T. niger the junction of these two bones is situated about a quarter of an 

 inch behind the anterior end of the petrosal ; in T. calvus the line of division is 

 farther forwards, nearly on a line with the anterior extremity of the petrosals : this 

 produces also a difference in the shape of the basisphenoid ; it is a triangular bone in 

 T. calvus ; in T. niger it ends in a point anteriorly in the same way, but it has parallel 

 margins from behind the points where the pterygoids lose their connection with it. 



If the existence of tlie crista galli and tlie grooving for tlie optic chiasma prove to be 

 really differential characters, they are particularly interesting from the fact that they 

 occur in the Gorilla. The nasal hone in the skull of " Sally " was distinctly ridged in 

 the middle line ; this character, however, was not found in the two skulls of T. calvus in 

 the Natural History Museum nor in any of the skulls of T. niger. This character is 

 also of some little interest, as it occurs in the Gorilla, and is indeed mentioned by 

 Owen as one of the points of distinction between these Anthropoids. In T. calvus 

 the spheno-maxillary fissure is very wide and continuous with the groove lodging the 

 orbital branch of the trigeminus. In T. niger this groove is not always open behind : 

 in tlie male Chimpanzee skull belonging to the Society the groove in question is 

 connected posteriorly into a tube by the complete closing in of the walls ; and in other 

 specimens of T. niger I found a partial indication of such a closing in. In the male 

 Chimpanzee just referred to, the spheno-maxillary fissure is remarkably narrow, 

 instead of presenting the appearance of a deep wide gash. And this apparent differ- 

 ence between the two species is very clearly marked in the two skulls belonging to 

 the Society ; but it will probably require revising when a large number of skulls are 

 available. 



No doubt it would be possible to institute a more detailed comparison between the 

 two species ; but the above notes contain, I believe, the principal points of difference, 

 and I would submit that, taken collectively, they fully justify the separation of the two 

 Chimpanzees. It is now necessary to inquire how far T. calvus agrees with any other 

 " species " of Chimpanzee. 



Prof. Hartraann^ does not consider that any case has yet been made out for 

 dividing up the Chimpanzees, though admitting " that there are not inconsiderable, 

 and perhaps even specific, varieties from the ordinary type." He is inclined to allow 

 provisionally three varieties, viz. the typical form of T. niger, Giglioli's variety (which 

 may be the same as MM. Gratiolet and Alix's T. aubryi), and thirdly Duvernoy's 

 T. tschego, probably the same as the Chimpanzee " Mafuca " already referred to. What 

 claims has T. auhryi to be regarded as a distinct species 1 Of the external characters 

 our knowledge is far too incomplete to allow of an attempt to answer this question. 

 With regard to the skeleton, I do not find that the skull offers any character that one 

 can seize upon as being of specific value. The skull of T. aubryi is figured in four 



' " Anthropoid Apes." Int. Sci. Series. 



