38 



ËiNAE Lönnberg, 



very remarkable 1 ), Gephalophus now proves to be the most advanced 

 type of those mentioned here as far as the development of the inci- 

 sors is concerned. An arrangement of the enamel of the incisors in 

 such a manner as has been described above for Cephalophus melano- 

 rhoeus serves of course to keep the cutting edge of the teeth sharp 

 while the teeth are worn. The great value of this sharpness is appa- 

 rent, because, thanks to this, the animal is able to cut off pieces of 

 such fruits that constitute its food. 



It is evident that the brain of the above described specimens 

 could not be in very good condition as the specimens have been pre- 

 served in toto, but some short notes about this organ may never- 

 theless be of value as nothing is known before about it. In stage a. 

 the furrows do not seem to be developed as yet. The brain of stage b. 

 is figured from the side and the left half from above (fig. 23 a, b). In 

 this stage the mesencephalon is not yet covered by the prosencepha- 

 lon. On the side of the prosencephalon a triangular depression is 

 seen, which corresponds to fissura Sylvii. The upper point of this 

 triangle is according to Kriteg's 2 ) terminology processus acumimis. The 

 anterior and posterior lower angles are produced resp. in proc. anterior 

 and posterior as the author quoted describes from the sheep-foetus. 

 The processus posterior is confluent with and continued without inter- 

 ruption with the fissura po'strhinalis to the posterior end of prosence- 

 phalon. In this respect the brain of this Cephalophus seems to differ 

 as well from that of sheep and ox (Kktjeg 1. c.) as that of Ouibos 3 ). 

 In the middle of the triangular depression the uncovered insula Re Hi 

 is seen. Higher up on the lateral side of the prosencephalon sulcus 

 suprasylvius is seen. At its posterior end it is forked. The upper 

 branch of this fork corresponds to what Krueg has termed processus- 

 posterior s. ss. The lower branch of the fork extends somewhat more 

 downwards and backwards than in the sheep and ox (Krueg) but less 

 so than in Ouibos (Retzius) or Sus. It is however probably an an- 

 cient characteristic. Rogner 4 ) found in some instances such a branch 

 also in the sheep. The anterior continuation of the sulcus suprasylvius 



1 ) Compare descriptions and figures in my paper. »On the Structure and Anatomy 

 of the Muskox». Proc. Zool. Soc. London 1900. 



2 ) Ueber die Furchung der Grosshirnrinde der Ungulaten. Zeitschr. f. wiss. Zool. 

 Bd. XXXI. Leipzig 1878. 



s ) Comp. Retzius: Biol. Unters. N. F. Bd. IX N:o 8. Stockholm 1900. 

 ') Zeitschr. f. wiss. Zool. XXXIX. Leipzig 1883. 



