52 



MR. C. S. TOMES OX THE 



[Jan. 16, 



seen to rlo so in text-fig. 16 ; in text-fig. 15 one or two penetrate 

 a. very little wfiy. 



In text-fig. 17, the enan)el of an Ocelot, I have drawn an 

 example of a greater penetration of the enamel by dentine tubes : 

 this, 1 may say, is the section which shows this to the greatest 

 extent out of some sixty sections taken from different genera of 

 Carnivora. But though, on the whole, this slight rudimentary 

 degree of penetration is perhaps rather moi'e frequent in Carnivora 

 than in most mammalian orders, in none does it occvir to an extent 

 in the least comparable with that found in Marsupials. 



The Enamel op Oreodonts. 



The examination of fossil teeth presents greater difiiculties 

 than that of recent teeth. Structurally, the enamel is always 

 well preserved, but it has in the process of mineralisation often 

 become unduly transparent, so that careful illumination is even 

 more essential in deciphering its sti'uctui-e. And the teeth ai'e 



Text-fig. 18. 



HyanodoH. — Transverse section. The enamel prisms are arranged in bundles 

 radiating so as to present a goblet form. In the dentine, not very well preserved, 

 the excavations of a fungus are seen. 



often exceedingly brittle and friable, so that it is difficult to get 

 good sections ; this can be partly overcome by imbedding the 

 teeth in desiccated Canada balsam before grinding them down. 

 The dentine, however, being richer in organic matter, is often 

 very badly preserved, so that sometimes all structure has dis- 

 appeared ; a fact which handicaps the obsei'ver in tracing the 

 passage of tubes fi-om it, and sometimes leaves him only able to 

 look for characteristic appearances of tubes in the enamel itself. 

 Moreover, many of the teeth being rare, only small bits or 



