NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN 39 



ACHAENODON INSOLENS " Cope, 1873 



Type. — Right and left rami of the mandible with the canine, P3, and 

 the last two molars represented, A.M. No. 5143. 



Horizon and locality. — Washakie B, "Mammoth Buttes," Washakie 

 Basin, Wyoming. 



Discussion. — Achaenodon insolens, the first described species, 

 would appear to be a slender- or shallow-jawed form with relatively- 

 elongate molars. The type, according to Granger's listing (1909), is 

 from the upper or B horizon of the Washakie beds, but lower-jaw 

 material from the Uinta B was referred by both Osborn (1895) and 

 Peterson (1919, fig. 11) to this species. 



MEASUREMENTS IN MILLIMETERS OF DENTITION IN TYPE SPECIMEN OF 



Achaenodon insolens, a.m. no. 5143 



Length of lower cheek tooth series, C (at alveolus)-M3, inclusive... 210.0a 



Length of lower cheek tooth series, anterior margin of alveolus for 



P2 to posterior margin of Ms 180.0a 



Lower molar series, anterior margin of alveolus for Mi to posterior 



margin of M3 92.0a 



P3, anteroposterior diameter : transverse diameter 24.0 : 17.5 



M2, anteroposterior diameter : transverse diameter of talonid 26.7 : 22.5 



Ms, anteroposterior diameter : transverse diameter of trigonid 40.0 : . . . . 



a. Approximate. 



ACHAENODON ROBUSTUS i^ Osborn, 1883 



Type. — Greater portion of the skull and the right ramus of the 

 mandible, P.U. No. 10033. 



Horizon and locality. — Washakie B, near Haystack Mountain, 

 Washakie Basin, Wyoming. 



Discussion. — Peterson (1919) regarded this species as distinct from 

 A. iitsolens largely on the basis of the deeper jaw with somewhat 

 shorter molars and relatively larger premolars, particularly P4. Shal- 

 lowness of the jaw in the type of ^. insolens might have been re- 

 garded as immaturity, but the referred specimen figured by Peterson 

 certainly exhibits well-worn teeth. The differences outlined may be 

 no more than might possibly be accounted for in individual variation ; 

 however, it would appear that A. robustus is somewhat more advanced 

 along the line of development followed in the achaenodonts and some- 

 what farther removed from Parahyiis than A. insolens. 



1* Illustrated in Cope, 1884, pis. 57 and 57a. 



15 Illustrated in Osborn, 1883, pi. 6 ; and Peterson, 1919, pi. 39, figs. 1-3. 



