4 ARKIV FÖR ZOOLOGI. BAND 7. N:0 G. 



which m^ is appearing but not yet fully developed;^ — »n. ad.» 

 = nearly adult) for animals in which m^ protrudes from the 

 socket but is not yet worn; »ad.» (= adult for animals in which 

 m^ is in use; »old» for animals in which m^ is much worn. 

 This gradation is, however, not quite suffieient, especially 

 the sign »ad.» has had to be applied to animals in rather 

 different stages of development. but it has been difficult to 

 find any better gradation for the present. 



The material of skulls of the Potamochoerus porcus-grou^ 

 which has been available for a more or less close examination 

 comprises more than a dozen and a half of specimens, six of 

 which have been females, and they are from different loca- 

 lities, from Liberia to the interiör af Cameroons. Considering 

 the different age and sex there is on the whole a rather 

 good correspondence between the dimensions of these speci- 

 mens. The upper mesial length from the occipital crest to the 

 tip of nasals of fullgrown male skulls appears to be as well in 

 Liberia as in Cameroons about 362 — 365 mm. The width of the 

 parietal flat area^ över which the temporal muscles do not ex- 

 tend is rather broad but varying from 58 to 40 mm., both extre- 

 mes being found in Cameroons (resp. »South Cameroons» ändat 

 Sembe S. af Sanaga). In younger specimens this measurement 

 is considerably smaller, as is found in the »nearly adult» but 

 rather young skull from Gaboon in which it is only 36 mm. 

 It thus approaches, as could be expected, the corresponding 

 measurement of the female skulls which themselves also are 

 rather similar in Liberia and in Cameroons till the latter 

 have grown old when the parietal breadth increases a great 

 deal. Already in a quite young female from Debundscha, 

 Cameroons, with an upper mesial length of the skull of only 



^ Still younger skulls have not been measured- 



" This characteristie appears to be rather constant and thus of consi- 

 derable taxonomie value in this genus as it also has proved to be in the 

 Wart-Hogs (Phacochoerus) It must be remembered, however, that males and 

 females of the same race often are different from each other and therefore 

 only members of the same sex have to be compared with each other, Es- 

 pecially the males exhibit the distinguishing racial characteristics, and the 

 females are much more similar inter se which is to be expected as they 

 represent an earlier and less specialised stage of development. Nevertheless, 

 M^hen the females of a broad-headed race have attained a high age the pa- 

 rietal area increases in breadth so that it resembles the same of the males. 

 This can be seen on the table of measurement (I) with regard to a specimen 

 of P. porcus pictus from Cameroons and also on the other table of measu- 

 rement (II) regarding an old female of the P. choeropotamiis group from 

 Natal, 



