KUNGL. SV. VET. AKADEMIBNS HANDLINGAE. BAND 58. N:0 2. " 85 



XII, fig. 3), which almost has the shape of such an accessory column as is to be found on 

 the inside of the molars of certain Ruminants. This anterior column of the first premolar 

 of these Antelopes is, however, not homologous with such accessory columns of the mo- 

 lars, but I consider it as a remaining rudiment corresponding to the anterior lobe of the 

 tooth which is present in the milk-premolars, but usually entirely lost in the permanent 

 premolar. In skulls of Connochcetes and Buhalis which I have examined there is no such 

 columnar appendix at the f rontside of the first premolars, nor is there anything like that 

 to be seen on the same teeth of a skull of Damaliscus lunata. This may thus be a char- 

 acteristic of the korrigum. 



Another striking characteristic of these skulls is found in the shape of the posterior 

 choanse (PI. XII, fig. 3). This peculiarity consists thereia that lamiTicepterpgoidece internee 

 some way behind hamuli pterygoidei are very strongly convex in the middle on their 

 inner, and concave on their outer side. By this bulging inwards of the middle of the 

 pterygoid walls of the choanse, although the free brims of the same are turned out to the 

 same width as anteriorly, the passage through the choanse must be much obstructed. 

 At the narrowest place this passage between laminae pterygoidece internee measures only 

 6 mm. and when in lifetime the bones are covered by the mucosa the interspace must 

 be nearly blocked up. The inner breadth of the choanse behind the palatal margin and 

 to the hamuli pterygoidei is about 20 — 22 mm. The lower margins of laminae, pterygoidece 

 internee have an interspace behind the Aam^Zi of about 27 mm., but this interspace decreas- 

 es gradually in a backward direction to 16,6 mm. Laminae pterygoidece externce extend, 

 however, beyond the lamince internee and form the free margin. The distance between 

 these free brims is about 31 — 32 mm. from behind the hamuli and continues for some 

 distance beyond the place where the narrowest constriction between laminae internee is 

 situated, then it gradually diminishes to about 26,5 mm. and is 30 mm. at the posterior 

 end of the choanse. These measurements are from the largest of the male skulls the 

 dimensions of which are recorded above. 



In the skulls of Connochcetes and Buhalis examined no such constriction of the choanse 

 has been observed, nor in Damaliscus lunatus, although the brim formed by laminae 

 pterygoidece externce may be more or less turned out. Especially in the latter this is 

 the case in a considerable degree. 



The question then readily presents itself: what purpose does this strange shape 

 of the posterior choanae serve? The reply to this appears most probable to be that the 

 shaping of the choanse is a secondary product without certain aim, but that the primary 

 thing is the strengthening of the pterygoid bones which serve for the insertion of musculi 

 pterygoidei. This purpose is fulfilled not only by these bones being remarkably thick 

 and solid, but also by their greater extension. The area of the bones is namely increased 

 both by the concavity of the pterygoid wall and the turned out brim. The combination 

 of these two conditions give the bony pterygoid wall a more solid construction and thus 

 more power of resistence against the pull of the mmsculi pterygoidei, when these contract 

 themselves. As these muscles are of great importance for the grinding of the food it is 

 easy to understand that an increase of them is of importance for the animal when it has 

 to masticate coarse food. Thus increased exercise of these muscules has been needed 



