50 



S. TOMES OX THE 



[Jan. 16, 



dentine surface. Towards the neck of the tooth enamel without 

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



Dasyurus enamel resembles that of Thylminus pretty closely, 

 though the tubes generally reach further thi-ough the enamel 

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



The Examel of Carxivora. 



As an illustration I have selected tliat of the Hyaena (text- 

 figs. 15 k 16), though it may be premised that th.e enamel 

 patterns of Carnivora 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, however, the enamel is thicker, the 

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

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



Text-fiir. 15. 



Hyaena.^ — Longitiidiiuil 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 laj'er. The enamel prisms are arranged in 

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



Two figures are given to show the difference in pattern Avlien 

 the enamel is viewed in a longitudinal and in a transverse section 

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

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

 diificult to discriminate between differences due to differences 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 straight course, and that all do not pursue 

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

 sheaves of prisms pui-suing an approximately parallel course, whilst 

 towards \\\q exterioi- of the enamel all the biuidles become parallel 



