FORT UNION OF CRAZY MOUNTAIN" FIELD, MONT. 



193 



7. Proliferation of accessory cuspules, from practically nil (e. g., 

 Chriacus) to considerable and distantly approaching the multicuspid 

 "arctocyonines" (e. g., Metachriacus). 



8. Development of hypocones on upper molars from practically 

 nil (e. g., Deltatherium) to pronounced (e. g., Chriacus). 



Other characters, known in fewer genera, also seen to be highly 

 distinctive, such as the molarization of upper premolars, width of 

 external upper molar shelf, shape of paracone and metacone, and 

 many other characters. 



Table 38 contrasts the genera of this complex that occur in this 

 fauna, and those most likely to be confused with them, as regards 

 these characters. 



Table 38. — Comparison of dentition characters in six genera of Oxyclaeninae 



Genus 



Chriacus.. 



Metachriacus... 

 Trkentes 



Minwtricentes . . 

 Spanoxyodon... 



Prothryptacodon 



Canine 



Moderately procum- 

 bent. 



Cf. Chriacus 



Crown vertical 



Cf. Tricentes 



Cf. Chriacus 



Strongly procumbent, 

 root extending be- 

 neath premolars. 



Present. 



.do. 



Pi absent.. 



Present 



Pi-2 absent- 

 Present 



Diastemata 



Slight or none 



Cf. Chriacus 



Short, C-P2.. 



None 



Long, C-Ps 



Very slignt, around 

 Pi, P2. 



P4 



Slender, with small, dis^ 



tinct metaconid. 

 Cf. Chriacus. 

 Stouter, no metaconid. 

 Cf. Tricentes. 

 With metaconid larger 



than in Chriacus. 

 Slender, metaconid 



barely incipient or 



absent. 



