26 ARKIV rÖR ZOOLOGI. BAND 3. N:0 8. 



(fig. 9 d). As the dentine forming the little crown is whiter 

 than cement, this is quite conspicuous even to the naked 

 eye. I ha ve tried to find out whether there was any rudi- 

 mentary cap of enamel covering the cusp, or not, and I have 

 for that purpose prepared longitudinal sections. My endea- 

 vours were not successful and I did not find any distinct 

 layer of enamel. Nevertheless, there cannot be any doubt 

 about the former existence of an enamel cap. 



From these facts, the shape and appearance of the small 

 teeth and the structure of this small unworn crown of a 

 somewhat larger tooth 1 think the following important con- 

 clusions may be drawn. 1) The ancestors of Orycteropus have 

 had teeth with a structure similar to those of other mammals. 

 2) The permanent teeth of the present Orycteropus are homo- 

 logous with the roots only of other mammalian teeth, that 

 is, with the exception of the very sliort, conical little crown 

 extending above the collar of cement and which very soon 

 is worn off and must be regarded as a rudiment. 



The latter thesis is in so strong opposition against the 

 views of all authors who have written about this subject 

 that it may need to be discussed a little more explicitely. 



CuviER^ pointed out that the teeth of Orycteropus had 

 a very extraordinary structure and differed from those of 

 other mammals. He described the »petits tubes paralléles» 

 extending all through the teeth, and finish es his description 

 with the words: »Il n'y a aucune racine». 



DuvERNOY - ga ve låter a detailed description of the struc- 

 ture of the teeth which in most parts is quite correct. He 

 repeated that — — — »ces molaires n'ont pas de racines» 



and maintained the opinion expressed by Owen be- 



fore, — »que chaque prisme qui entré dans la compo- 



sition d'une arriére-molaire d'Orycterope, est une dent parti- 



culiére» — — — but added, against Owen, — » que 



chacune de ces dents séparées est composée uniquement d'i- 

 voire ou de dentine, et qu'elles ne sont pas liées entré elles 

 par du cement.» 



1 Rech. sur les Ossem. Foss. T. V. part 1, ed. 3. Paris 1825 p. 134 

 135. 



2 Mém. sur les Oryctéropes. Ann. Se. Nat. Ser. 3, T. 19. Paris 1853. 



