KUNGL. SV. VET. AKADEMIBNS HANDLINGAR. BAND 58. N:0 2. 



93 



up in both jaws. Thus the increase in size between this stage and the fully adult cannot 

 be expected to be very great, and therefore the measurements recorded below can be 

 compared without being misleading. 



Distance between alveolar margin of m' and orbit 



Breadth across outside of m* 



Length of nasals 



Greatest transverse diameter of m* 



» m' 



» TOj 

 » TO, 



The shape of the bones of the two skulls is in many cases very different. The an- 

 terior contour of the palatal bones of the skull from Beni forms an evenly curved arch 

 extending forwards to a level with the anterior portion of w}, but in the castaneus from 

 Mukimbungu it is a straight transverse (22 mm. long) line on a level with the anterior 

 portion of m% and the lateral sutures of the palatal bones form distinct angles with this 

 anterior transverse suture. The posterior choanae are much narrower in the larger skull 

 measuring on a level with the posterior end of m' only 8,7 mm., but in the smaller female 

 skull from Beni the same measurement is 14 mm. This depends upon the fact that in the 

 former the pterygoid laminse stand vertically, in the latter they diverge towards their 

 lower margin. 



The shape of the nasals is also very different. In the castaneus skull the posterior 

 ends of the nasals project with a blunt point backwards between the processus nasales of 

 the frontals, which latter are broadly truncate and form an almost straight transverse 

 suture with the lateral portions of the nasals (PI. XI, fig. 2). In the female skuU from 

 Beni the nasals are rather broadly rounded behind, occupying almost the whole upper 

 surface, but the processus nasales of the frontals extend forwards on both sides with sharp 

 point^ which cut deeply into the nasals between their upper horizontal and lateral ver- 

 tical portions (PI. XI, fig. 3). The premaxillaries do not reach the nasals in C. c. arrhenii 

 (cf. fig. 3). 



The horns of castaneus from Mukimbungu are much longer (about 5,5 cm.) which, 

 of course, as being a male characteristic is of no importance for this compa;rison, but they 

 are smoother all over and quite circular in section. The short (2 V^ cm. ) horns of the fe- 

 male from Beni are not only transversely more rugose, but display also longitudinal rid- 

 ges, so that the section is not round. The female from Beni has also the horns more raised 

 so that they form a distinct angle with the frontal plane (PL XI, fig. 3), while those of 

 the castaneus buck slope evenly, with the frontal plane (PL XI, fig. 2). 



The angular flange of the mandible is much more sharply set off (PL XI, fig. 3) 

 in G. c. arrhenii than in C. castaneus from Lower Congo (PL XI, fig. 2). 



The colour of the specimen from Beni is much darker than that of the castaneus 

 from Mukimbungu. The general chestnut colour proves at closer inspection to be thinly 



