200 Wortman — New American Species of Amphicyon. 



Art. XVI. — A New American Species of Amphicyon ; by 

 J. L. Wortman. 



The true genus Amphicyon has not hitherto been found in 

 this country, notwithstanding the fact that Leidy, Cope, and 

 Marsh have, at various times, referred certain specimens of 

 extinct dogs, having three true molars in the upper jaw, to this 

 group. Scott has satisfactorily shown that all the Amphi- 

 cyons of the American Tertiary heretofore described, belong 

 to genera quite different and distinct from the typical genus 

 Amphicyon of Europe. 



While recently engaged in the examination of some remains 

 of extinct Canidae in the Marsh Collection at the Peabody 

 Museum, I came across a beautifully preserved palatal portion 

 of a skull, from the Loup Fork Miocene deposits of Nebraska, 

 which I do not hesitate to refer to this European genus. The 

 specimen in question includes all the superior series of teeth 

 with the exception of the incisors, a few premolars of the 

 right side, and the last upper molar of the left side. 



As compared with the best known European species, Amphi- 

 cyon giganteus Laurill., from the Middle Miocene of France, 

 great similarity of structure is at once apparent. Like all the 

 Amphicyons the canines are unusually large and robust and 

 are provided with prominent cutting edges, both anteriorly and 

 posteriorly. The three anterior premolars are strikingly 

 reduced in size, the two anterior being separated from each 

 other and from the succeeding teeth by short diastemata. The 

 first premolar is implanted by a single fang, the second and 

 third by two. In comparison with the other teeth, the fourth 

 premolar, or superior sectorial, displays about the same propor- 

 tions as that of A. giganteus, but the internal cusp is less dis- 

 tinct ; it appears as a low rounded swelling at the base of the 

 crown, supported by an independent root, and is not so distinct 

 as is usual in the Canidae. The molars differ considerably 

 from those of A. giganteus in that the external portion of the 

 crown is less rounded, has a greater fore and aft extent and 

 the internal less, giving to it a more distinctly triangular 

 appearance, as in the true dogs. Another important difference 

 is seen in the prominence and external position of the basal 

 cusp at the antero-external angle of the first molar in the 

 American species, in marked contrast with the internal posi- 

 tion and more reduced character of this element in the Euro- 

 pean species. It may be remarked that in their general 

 appearance the molars of the American form are decidedly 

 more dog-like, while those of the European species more closely 

 approach the structure displayed by the primitive bears. 



