LÖNNBERG, ON A NEW ORYCTEROPUS FROM NORTHERN CONGO. 31 



sists only of cement wliich substance also forms an outer 



layer around the sides of the root. The coronal and central 



part of the pulp is irregular, but in the most basal part of 



it the nutritive canals seem to have a tendency to arrange 



themselves longitudinally. — When the period of growth tjf 



the teeth was extended the roots became gradually more 



open and the pulp suffered a displacement towards the base. 



In a tooth representing almost 



the same stage as the one figured 



in fig. 9 c, the basal end has the 



appearance shown in fig. 12. As 



may be seen there is a large open 



cavity at the very end of the 



tooth, which has been occupied 



by the main pulp. From this 



cavity the nutritive canals branch 



off through large and small aper- 



tures in the dentine mäss. The 



large canals then branch into 



smaller and gradually assume the 



straight longitudinal course. 



The basal ends of the molars 

 are modified still further. There 

 cannot be spöken of any main 

 pulp. There is no common cavity 

 but the end is just as of ten con- 

 vex as concave. The canals open 

 directly upon this basal surface 

 and are thus more independent 

 of each other. It cannot be doubt- 

 ed, however, that these openings 

 of the canals are homologuous 



with the apertures from the basal cavity of the tooth shown 

 in fig. 12 and thus the gradual change may be understood. 

 The dentine surrounding each nutritive canal takes the 

 hape of a more or less regular prism and these prisms are 

 of ten, especially in the most specialised teeth, a hexagonal. 

 This rule is, however, by far not Avithout exceptions and at 

 the side of the regular and irregular hexagonal prisms there 

 are seen pentagonal quadrangular etc. A look at the hind- 

 ends even of the most specialised teeth, the molars, reveals 



Fig. 11. Longitudinal section 

 through the tooth represented 

 in Fig. 9 a. Strong] y enlarged. 



