450 SCIENCE PROGRESS 



vations of Dr. F. Ameghino, they have also a fuller series of 

 successional teeth. 



These features, coupled with the marked general resemblance 

 of the sparassodonts to the creodonts, might well make us pause 

 before giving adherence to the views of Mr. Sinclair. But, 

 probably while his memoir was in the press, a new factor has 

 been introduced into the question. In a paper read before the 

 London Zoological Society in January last, Mr. C. S. Tomes 

 announced that microscopic examination of sections of the teeth 

 of creodonts and sparassodonts revealed the fact that in internal 

 structure the enamel of these is of the type characteristic of 

 modern Carnivora, and quite different from that of marsupials. 

 He concludes by the statement that, while in one feature the 

 enamel of the teeth of the Carnivora may possibly indicate 

 remote marsupial affinity, yet in this respect creodonts (and 

 sparassodonts) carry us no farther than their descendants, the 

 recent members of the order. 



If these conclusions are well founded, the case for the marsu- 

 pial nature of the Patagonian sparassodonts will, at any rate, 

 have to be reconsidered. 



The reference to Mr. Tomes's paper has introduced the 

 question of the affinities of the true creodonts (altogether apart 

 from whether sparassodonts are members of that group or 

 marsupials) ; and to this subject Mr. W. D. Matthew, of the 

 American Museum, has made a contribution in a paper published 

 during the year in the Proceedings of the United States National 

 Museum (No. 1449), under the title of " The Osteology of Sinopa, 

 a Creodont Mammal of the Middle Eocene." After referring to 

 Dr. Wortman's view that creodonts and modern carnivores are 

 divergent branches from a Cretaceous marsupial stock, the author 

 expresses himself as follows: "I think it safe to say that if we 

 set aside superficial and adaptive characters, and rest principally 

 upon deep-seated resemblances, such as are found in the characters 

 of the base of the skull, the dental and dorso-lumbar formulae, 

 etc., we find every known creodont very much nearer to the 

 modern Carnivora than to the modern marsupials. On the other 

 hand, the little that is known of Cretaceous marsupials bears 

 distinctly the marsupial stamp in every detail, and does not show 

 any approach to the early placentals." 



It is thus evident that the creodont-sparassodont-marsupial 

 question is one that is very far from approaching a settlement ; 



