b OYLDENSTOLPE, ON A COLLECTION OF MAMMALS MADE IN EASTERN AND CENTRAL BOKNEO. 



amount of variation as to its size. The absence of some of the molars is a thing 

 very seldom met with among the Anthropoid Apes and it seems to indicate that the 

 third molar is on the way to become functionless. On the contrary one or two 

 supernumerary molars are of ten found among the Anthropoid Apes as has been shown 

 to be the case with the Orang Utan, the Chimpanzee and the Gorilla. 



In the Bornean Gibbon there seems to be a variation with regard to the teeth 

 in two different ways viz. partly an evidentty indi vid ual anomaly conspicuous by the 

 abscence of some the of molars and partly a variation iri size of the molars. The 

 former anomaly cannot be of any taxonomic value but the latter exhibits diffe- 

 rences, analogous to such which are of ten used for distinguishing different geo- 

 graphical races or even species. 



In another specimen (female) there are only three incisors in the upper jaw, 

 the outer one on the left side being absent. In this same specimen there is still 

 another anomaly on the same side of the upper jaw viz. a supernumerary canine, 

 and this tooth is of about the same size and shape as the ordina^ one. 



In the following table I have put together some measurements in millimeters 

 taken on the teeth of the fullgrown specimens in Mr. Lumholtz' collection: 







o" 



ef 



ef 



ef 



ef 



ef 



ef 



Q 



-t- 



O 



9 



Transverse breadth 



of pm 1 . . 



5,1 



4,5 



5,0 



4,1 



4,2 



4,8 



4,5 



4,1 



3,8 



4,1 



» » 



» pm'-' . . 



5,3 



4,6 



5,3 



4,8 



4,-1 



4,0 



5,1 



4,2 



4,2 



4,2 



» » 



ra 1 . . 



G,3 



6,1 



5,7 



5,5 



5,8 



5,8 



0,5 



0,1 



5,9 



5,5 



» » 



m'"' . . 



6,3 



6,2 



0,3 



0,1 



0,2 



5,5 



7,2 



0,2 



5,8 



5,5 



» » 



» m 3 . . 



5,3 



5,8 



5,2 



5,3 



4,9 



0,1 



6,6 



0,2 



5,3 



absent 



» » 



» pm, . . 



4,6 



3,8 



3,0 



3,3 



4,9 



3,5 



4,2 



3,9 



3,2 



3,4 



» » 



» pm 2 • ■ 



4,0 



3,6 



3,'J 



3,9 



4,8 



4,0 



4,6 



3,3 



3,2 



4,1 



» » 



» m, . . 



4,9 



4,7 



4,4 



5,0 



4,8 



4,9 



5,1 



5,1 



4,9 



4,9 



» » 



» m t . . 



5,8 



5,3 



5,4 



5,2 



5,3 



5,6 



0,1 



5,1 



5,3 



5,2 



» » 



» m 3 . . 



5,1 



5,2 



4,8 



5,2 



5,0 



5,2 



5,8 



4,8 



4,8 



4,8 



The brain capacity of the Bornean Gibbons has been measured by means of 

 hemp seed, since the jissura orbitalis etc. has been closed with some cotton and the 

 following results have been obtained. 



The largest brain capacity is possessed by an immature male specimen, in 

 which none of the molars are perfectly developed. The first upper molar has, 

 however, b röken through the gum and is clearly visible, though still not functional. 

 In this specimen the brain cavity has a capacity of 108 ccm. Among the fullgrown 

 male series in the present collection there is a certain amount of variation as to the 

 capacity of the brain cavity. Thus it varies between 72 ccm. to 106 ccm. or 72> 

 82, 85, 90, 92, 105 & 106 ccm. respectively. 



I have only been able to measure the brain capacity of a single adult female 

 and in that specimen it measures 83 ccm. A semiadult male specimen has a brain 



