LÖNNBERG, ON A NEW ORYCTEROPUS FROM NORTHERN CONGO. 29 



sucli kind as could be produced, viz. dentine and cement, in 

 the lower or alveolar portion of each tooth. The teeth be- 

 came thus more and more lengthened and continued to grow 

 for a longer period which by and by increased till the pre- 

 sent stage of uninterrupted growth during the whole Hfe was 

 reached. The pulp had, to begin with, short and irregularly 

 branched nutritive canals entering the dentine. When the 

 growth increased more and more rapidly and the teeth 

 became more and more columnar the direction of these 







A 





Fig. 10. Transversal (a) and longitudinal section through a part of the 

 tooth represented by fig. 9 d. Strongly enlarged. 



canals must be chiefty longitudinal. To use a likeness, in- 

 stead of forming a bush with sho-rt irregular branches they 

 formed a pyramidal Italian poplar with long parallel branches. 

 An investigation of the supernumerary teeth belonging to 

 the milk-dentition proves this, becanse they furnish with inter- 

 mediate stages in which the canals are not so regularly longi- 

 tudinal. Even if we choose one of those which most nearly 

 resemble the permanent teeth the regularity of the longitudi- 

 nal canals is not very perfect. A transverse section shows. 



