40 EINAR LONNBBRG, MAMMALS COLLECTED BY THE SWEDISH ZOOLOGICAL EXPEDITION ETC. 



size better with the specimens described from Baringo and Nandi by Elliot under 

 the name of P. furax. But strange to say there are to be seen among the skulls 

 from Guaso Nyiri not only such differences which can be explained as due to indi- 

 vidual variation but also others which appear to be of more importance. The diffe- 

 rences between the skulls of different ages are fully shown by the dimensions of the 

 skulls a and b as recorded in the accompanying table of measurements. These two 

 specimens (PL I fig. 4 & PL II figs. 1 & 2) were shot in the same place and out of 

 the same herd on the north bank of Guaso Nyiri some distance below Chanler Falls. 

 Specimen a is a very old male (PL II fig. 1) with the canines worn off to the same 

 level as the other teeth which all of them are strongly worn, and the lower incisors 

 have even disappeared. Specimen & is a fully adult male (PL I fig. 4, PL II fig. 2) 

 in its prime of life. Its formidable canines are about 40 mm., and the molars are 

 very little worn but the incisors somewhat more. It is evident that the differences 

 between skulls a and b are due to age, and a comparison of their dimensions reveals 

 the differences which are connected with increasing age. 



Specimen c is a rather old male (PL I figs 2 & 3) with incisors as well as mo- 

 lars strongly worn. The canines are also worn down to a length of about 33 mm. 

 Specimen c is intermediate in age between a and b, and thus if a dimension in c is 

 intermediate between the corresponding ones of a and b, this is evidently a dimen- 

 sion which alters with increasing age. A fine example of this is the distance between 

 the last molar and the posterior border of the palate. But there are other dimen- 

 sions of this skull c which are not intermediate between those of a and b, nor similar 

 to either of them, and the differences thus exhibited by skull c appear to be of more 

 importance than the others. 



These differences in dimensions indicate that specimen c has a shorter muzzle 

 so that the distance from the mesial point of the superciliary ridge to the lip of 

 the premaxillary is considerably shorter than in specimens a and b. The nasals (if 

 measured in a straight line) are also shorter in the former than in the two latter (conf. 

 the table). The shortness of these measurements is, however, partly due to the fact 

 that the orbits are more abruptly raised in c (PL I fig. 3) than in a and b (PL I 

 fig. 4) and the facial surface of the orbital walls forms almost a right angle to 

 the flat upper surface of the muzzle in c, while the same angle is somewhat more 

 obtuse, and the profile on a level with the orbits more slanting backwards in a 

 and b. But the muzzle is really shorter in c than in a and b as is proved by com- 

 paring the respective distances from the middle of the lower border of the orbit to 

 the tip of the nasals (conf. the table). Skull c is also considerably broader across 

 the orbits than skulls a and b. This is due to the great breadth of the facial sur- 

 face of the outer walls of the orbits in c, because the inside distance between the 

 lateral walls of the orbits is even a little shorter than in a and b. 



Although these cranial differences are not very great, they appear to be of 

 importance, especially as they are supported by differences in the colouration of the 

 fur as well. Specimens c and d which were shot on the north bank of Guaso Nyiri 

 above Chanler Falls and only about one, or one and a half days march to the east 



