106 Mr. E. D. Cope on the 



Van der Hoeven lias given* descriptions and figures of the 

 skull and dentition of the Icticyon venaticus of Lund, of Brazil. 

 From these it appears that the present species differs from the 

 latter in the greater development of the inner part of the 

 tubercular molar of the superior series ; in /. venaticus this 

 part is much reduced. The tubercular molar of the lower 

 jaw is also much smaller in the living species, the angular 

 and coronoid processes less developed, and the condyle less 

 extended transversely. The cranium of the /. crassivultus 

 is much more robust, but not much longer than that of /. 

 venaticus. 



Discovered by J. L. Wortman in the Truckee beds of the 

 White-River Tertiary of the John-Day River region of 

 Oregon. 



General Observations. 



In both Canidss and Felidce the reduction of the dental 

 series is connected with a contraction of the facial part of the 

 skull, cither posteriorly or anteriorly. Enhydrocyon is an 

 example of anterior abbreviation and Icticyon of posterior 

 contraction among Canidaj, while Smilodon and Lynx exhibit 

 the anterior reduction in Felida?. I have already pointed out 

 that this reduction is accompanied by a corresponding increase 

 in the size of the sectorial teeth. But the reduction in the 

 number of teeth in geologic time has not been confined to the 

 Carnivora, but belongs to the Ungulates and Primates as well. 

 The small number of teeth is generally associated with high 

 specialization among Mammalia generally. The genera 

 Hynagodus and Dysodus are the most specialized of the 

 Canida3. 



I may here refer to the frequently observed reduced denti- 

 tion of man. Darwin first pointed out the significance of the 

 absence of the third molars from the standpoint of evolution, 

 citing American cases; and I have observed the similar 

 bearing of the absence of the external superior incisors f. 

 These reductions are very frequent in the United States, and 

 probably elsewhere among civilized nations ; but statistics on 

 this point are yet wanting. My friend Dr. C. N. Pierce, an 

 experienced and scientific dentist of this city, informs me that 

 he knows of twenty-eight families in which the external 

 superior incisors are absent ; to these, four families may be 

 added which have fallen under my own observation : that the 

 absence of one or both pairs of the third molars is still more 

 common, is confirmed by Dr. Pierce's experience. 



* " Over het Geslaclit Icticyon/' Wis. en natuurk. Verb, der Koninkl. 

 Akadetuie, Amsterdam, Deel iii. 



t Proceedings American Philosophical Society, 1871, p. 234. 



