44 EINAE LONNBERG, MAMMALS COLLECTED IN CENTRAL AFRICA. 



The dimensions of the brain-case of the female as expressed by the measurements 

 of the greatest width, the least postorbital width and the distance between the supra- 

 orbital ridge and the occiput (without crest) are very similar to those of the adult and 

 semiadult males, although the latter are a little greater than those of the female. 



The capacity of the brain cavity is in the young Baboon with milk-dentition about . . . 144 ccm. 



The same of the young male with first molar developed is about 155 » 



The same of the semiadult male with second molar developed is about 185 » 



The same of the adult male is about 185 » 



The same of the adult female is about 172 » 



Judging from external measurements of the skull it is rather surprising to find 

 that it is so much difference in volume between the brain-cavity of the adult male and 

 that of the female. It appears probably that this is due to the male brain-cavity being 

 wider behind in its occipital portion than that of the female. To prove this with exact 

 measurements is difficult without cutting the skulls, and this material is too precious 

 for that. As it has been stated above the adult female and the semiadult male (with se- 

 cond molar developed) skulls represent in several respects the same morphological stage 

 because the latter has not yet attained the great massivness of the bones found in the 

 adult male. It may therefore be assumed that in both the breadth of the squama occipi- 

 talis stands in the same relationship to the width of respective brain-cavities the wall 

 of which it forms. As the greatest breadth of the planum nuchale in the female skull is 

 74 mm., and that of the semiadult male is 85 mm., it may be concluded that the posterior 

 portion of the male brain-cavity is in a corresponding degree wider than that of the female. 

 This may be the explanation of the difference in volume of the brain-cavities as recorded 

 above. 



With regard to the stages of development of the dentition of the young Baboons 

 of this collection the following communications can be made. In the youngest skull 

 only the complete milk-dentition is present. 



In the next youngest skull, characterized by the presence of the first molars, the 

 permanent upper incisors are present, but the lateral pair has not attained full height. 

 In the lower jaw the median pair of permanent incisors have attained full size, but the 

 lateral pair are cutting the gum. The milk-canines and milk-molars are present in both 

 jaws. 



In the semiadult skull with the second molars developed no milk teeth are left; 

 the permanent incisors and premolars are fully developed, but the canines of the lower 

 jaw have not quite reached the height of the first premolar; and those of the upper jaw 

 are still shorter. 



Pafio tessellatus Elliot is of course nothing more than a geographical subspecies 

 of the same group of dark Baboons as P. doguera, furax etc. How far it is distributed 

 in its typical form is not yet known. I am, however, able to state that already atHoima 

 in the Uganda Protectorate the dark Baboons of this group are somewhat different. 

 This can be done because my friend Prof. Dr. Rob. E. Fries has kindly permitted me 

 to examine and measure the skull of an adult male Baboon which he shot some years 



