50 



MR. C. S. TOMES ON THE 



[Jan. r 



dentine surface. Towai-ds the neck of the tooth enamel without 

 tubes is, as in the Diprotodonts, to be found. 



Dasyunis enamel resembles that of Thylacinus pretty closely, 

 though the tubes generally reach further through the enamel 

 (text-fig. 14, p. 49). 



The Enamel of Carnivoea. 



As an illustration I have selected that of the Hysena (text- 

 figs. 15 & 16), though it may be premised that the enamel 

 patterns of Caxnivora are fairly constant. As one would expect 

 from analogy, they are not quite identical in all : thus in the Dog 

 group they are simpler, and where the enamel is thin the prisms 

 become quite straight. Where, hoAvever, the enamel is thicker, the 

 patterns are easily identifiable as similar to those found in, for 

 example, the Felicia?, though the curvatures are less pronounced. 



Text-fig. 15. 



Hya-iia. — Longitudinal section near apex of cusp. A few dentinal tubes pass a 

 little way into the enamel. Most of the dentinal tubes branch and terminate 

 in the minute spaces of the granular layer. The enamel prisms are arranged in 

 alteriiating bundles, and pass nearly at right angles to one another. 



Two figures are given to shov/ the difierence in pattern when 

 the enamel is viewed in a longitudinal and in a transvei'se section 

 of the tooth ; hence any obliquity in the plane of the section will 

 alter the appearances. But, after a little experience, it is not 

 difficult to discriminate between differences due to clifierences of 

 plane and thos.e due to real differences in arrangement. 



It will be noticed that no prisms in this, the thicker portion of 

 the enamel, pursue a stiaight course, and that all do not pursue 

 the same course. They are, however, grouped into bundles or 

 sheaves of prisms pursuing an approximately parallel course, whilst 

 towards the exterior of the enamel all the bundles become parallel 



