190 1.] Matthew, Additional Observations on the Creodonta. I J 



4. High compressed claw ; extension upward of distal facets of ist and 2d 

 phalanges and to some extent of distal metapodial keels. 



5. Slender, serrate, unworn canines. * 



6. Reduction of premolar dentition. 



7. Low-cusped quadrate molars, nig somewhat reduced. 



The first of these characters leads towards the Carnivora gen- 

 erally, except the sharp-keeled magnum, which seems to point 

 especially towards the Bears. It may, however, be merely the addi- 

 tional brace required for large-clawed feet. The semi-opposed 

 thumb is a character pointing towards arboreal types, hardly to 

 any known Ursidse. The proportions of the phalanges agree with 

 those of the Ursidse and of some other Carnivora {Frocyon, etc.). 

 The high compressed claw-phalanx suggests the Ursid^e very 

 strongly ; the greater extension of the facets is a modernization 

 common to all the sharp-clawed types. 



In the dentition all three characters point to the Ursidae and 

 to no other Carnivora. The elongation of the second molar after 

 the disappearance of the first is exactly paralleled by the Raccoons 

 in evolving from the Canidae through Phlaocyon — a very similar 

 adaptation not carried so far as in the Ursidae. 



The argument for placing the Arctocyonidae ancestral to the 

 Ursid^ is, then : 



1. They belong by their foot structure to the adaptive Creo- 

 donta, the teeth not placing them in either the adaptive or 

 inadaptive group. 



2. The three chief progressive characters of the teeth are those 

 which distinguish the bear dentition. ^ 



3. The claws are far advanced towards the type found in the 

 Ursidae and in hardly any other Carnivora. 



4. The one marked distinction that I can see to separate the 

 bear-carpus from that of other Carnivora is found in process of 

 formation in Clcznodon. 



5. The proportions of the digits show a specialization found in 

 the Bears and in hardly any other Carnivora. 



Against this may be urged : 



1. ClcBnodon has the thumb more opposable than in the modern 

 Ursidae. 



2. Anacodon has the premolar dentition as much reduced as in 

 the modern Ursidae. 



^January, igoj.] 



