GOO MB. J. THORNTON CARTER ON THE 



Tarsipes it is reduced to small limits " (Tomes, Dental Anatomy, 



The significance and value of these contributions lies in the 

 fact that Tomes demonstrated clearly that the enamel pattern in 

 Rodents provides a specific criterion of affinity, and that the 

 structure of the enamel in Marsupials, taken in conjunction with 

 other anatomical characters, may be employed to demonstrate 

 Marsupial relationship. 



Seventy years have passed since the publication of these 

 researches, but, in so far as I am aware, during that period no 

 one has extended Tomes's work and published the results of the 

 examination of the enamel structure in all the representative 

 members of a diversified order ; and further, with the exception of 

 Sir Charles Tomes, F.R.S., the distinguished son of a distinguished 

 father, no one has applied the results obtained to the determi- 

 nation of affinities or relationship in the case of extinct mammals. 

 In a paper on the " Minute Structure of the Teeth of Oreodonts, 

 with special reference to their suggested resemblace to Mar- 

 supials" (P. Z. S. 1906), Sir C. Tomes employed the character of 

 tubular enamel as a test of Marsupial relationship, and found 

 that in none of the Creodont teeth which he examined was this 

 character present. Included with this Creodont material was a 

 portion of a tooth of Borhyaina, one of the Sparassodonta, in the 

 enamel of which Tomes found no trace of tubes. But the 

 Marsupial characters of this group Avere so numerous that Prof. 

 D. M, S. Watson, F.R.S., asked me to undertake a further exami- 

 nation of the enamel in other members of the suborder, and I 

 was fortunate enough to discov^er this Marsupial character in the 

 teeth of Cladosictis, Pharso2)horus, and of Borhycena (Journ. 

 Anat. 1919). 



Following the provision of the material for the examination of 

 Sparassodont teeth, the authorities of the American Museum of 

 Natural History handed over to me a rich and representative 

 collection of teeth and jaws of Eocene mammals, comprising some 

 eighty genera, which had been formed for the purpose of obtain- 

 ing a set of sections with the hope that, in the words of 

 Dr. Matthew, "the investigation thereof will provide a new line 

 of evidence for the affinities of mammals, as distinct from the 



skeleton or the teeth or the soft anatomy" and to '' have 



a cross check on relations of the same kind as the cross check 

 betAveen teeth adaptations and feet adaptations." Already several 

 hundreds of sections have been prepared from this material, and 

 the results obtained encourage the hope that Dr. Mathew's exjDec- 

 tations will be fulfilled. To obtain the utmost value from such a 

 collection, it is desirable to possess a complete series of sections of 

 teeth of every genus of existing mammalia, and, in consequence, 

 I have laboured to build up a collection of ground sections which 

 should embrace not only representatives of each genus, but also, 

 in so far as is possible, sections of each tooth in the individual 

 dentition. 



