Material for the Study of Ruminants. 



37 



that did not develop further. That is, however, not the case. Sections 

 through the whole mandible of stage d. reveal that there are only to 

 be found rudiments (»Anlagen») of the four normally present teeth of 

 the milk-dentition and the small rudiments of the corresponding four 

 teeth of the permanent dentition. The fifth posterior papilla has no- 

 thing to do with those teeth. In stage d. the anterior median papilla 

 corresponding to the median incisor is the largest, because this incisor 

 is the largest, but the other four papillae are about equal. In stage e. 

 the teeth are beginning to cut the gum and can be felt with a pair 

 of pincers, the fifth posterior papilla is now the smallest. It is. however, 

 well conspicous even in later stages, for instance in stage f. (see fig. 10), 

 and also in stage but now it is quite evident that it has nothing 

 with the teeth to do as those arc already fully developed as far as 

 their visible parts are concerned. 



The structure of the incisors 

 of Gephalophus melanorhoeus is quite 

 interesting with regard to the distri- 

 bution and development of their 

 enamel. There is namely on the 

 anterior surface of the teeth quite 

 a thick layer of enamel all the way 

 to the cutting edge of the tooth. 

 But on the posterior or inner sur- 

 face of the incisor the enamel-layer 

 is of such extreme thinness that it 

 can be' said to be practically ab- 

 sent 1 ). This is thus a structure 

 that in some degree reminds one 

 of the same of the incisors of the 

 Rodents and it is much more ad- 

 vanced in such a direction than for instance the same of the lamb or 

 common calf. Concerning the two latter I have shown before, that 

 the enamel on the inner side of the incisors is strongly reduced if 

 compared with the condition prevailing in such a primitive Ruminant 

 as Ovibos, in which the difference in thickness of the enamel-layer of 

 the anterior and posterior (interior) surface of the incisors is not so 



) The préparâtes, on which this statement is based, have been made of the median 

 incisors of a foetus fully developed, but not yet born so that the absence of the enamel 

 could not be due to wearing! 



e. enamel la3'er of the outside. Longitudinal section 

 through incisor of Cephalophus melanorhoeus showing reduc- 

 tion of enamel on the inner side. 



