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BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



to other primitive arctocyonids and that the resemblance is purely 

 convergent, aside from the fact that both have the stereotyped pattern 

 of all these ancient forms. 



The canine, preserved in the type, has a large root and is curved in 

 a pronounced arc. The crown is unusually erect, as it is also in Tri- 

 centes. Pi is known only by its alveolus, which is single and rather 

 large. The premolars very closely resemble those of Tricentes, except 



Figure 53. — Spanoxyodon latrunculus Simpson, U.S.N.M. no. 9287, left lower jaw: a, Crown view; 6, inter- 

 nal view. Twice natural size. 



Figure bi.—Mimotricentes latidens (Qidley), U.S.N.M. no. 9269, left lower jaw: a, Crown view; 6, Internal 



view. Twice natural size. 



that the heel of P4 is more expanded transversely and its posterior 

 border is more nearly a straight transverse line — a distmction prob- 

 ably not generic, as it is closely similar to that between Metachriacus 

 punitor and M. provocator. The molars are even flatter and broader 

 than in Tricentes but otherwise closely resemble those of that genus 

 except for the difference in the paraconids. Upper teeth are known 

 only in one specimen, mentioned below. 



