NO. 8 UPPER EOCENE ARTIODACTYLA — GAZIN I9 



b. Three lower premolars. P4 enlarged. Paraconid and hypoconulid (ex- 

 cept M3) vestigial or absent. Lower C caniniform. 



(i) Molars relatively elongate Parahyus 



(2) Molars broad and premolar series relatively long Achaenodon 



3. Hypoconulid of Mi and M2 developed on crest between hypoconid and 

 entoconid. Talonid broadly basined. P4 without metaconid 



DiACODEXINAE 



a. Cusps sharply defined, paraconid and hypoconulid distinct. Hypocone 



of upper molars weak or absent Diacodexis 



b. Cusps inflated (both M* and M' believed to have hypocone). 



(i) Paraconid and hypoconulid distinct Wasatchia 



(2) Paraconid weak or absent and hypoconulid less distinct. .Bunophorus 

 B. Cheek teeth moderately to highly selenodont. 



1. Pi and lower canine approximately equal 



OROMERYCIDAE and probably Eocene CAMELIDAE 



a. Entoconid of lower molars isolated. Protocone of upper molars bilobed 



posteriorly OROMERYCIDAE 



(i) Enamel rugose. Upper molar teeth oblique, transversely com- 

 pressed posteriorly, and increasing in size from M* to M*. Ex- 

 ternal styles prominent Oromeryx 



(2) Enamel rugose to smooth. Upper molar teeth more nearly rec- 



tangular and increasing in size from M^ to M^. No significant 

 diastemata between premolars. External styles prominent 



Protylopus 



(3) Enamel rugose. Upper molar teeth nearly rectangular, not oblique, 



and more nearly equal in size from M* to M^. External styles 

 reduced and ribs much emphasized (lower teeth not known) 



Malaquijerus 



(4) Enamel comparatively smooth. Alarked diastemata between Pj and 



P3 (upper teeth not known) Camelodon 



b. Posterior crest of protoconid joined to metaconid and anterior crest 



of hypoconid joined to entoconid so that the trigonid and talonid 

 columns of the lower molars are separate enamel loops, joined only 

 by the lingual wall. Protocone of upper molars completely crescentic, 



not bilobed posteriorly Poebrotheriinae 



(i) Lower molars with weak metastylid flexure on lingual wall and 

 this surface is somewhat convex lingually over metaconid and 

 entoconid. M3 with hypoconulid loop. Upper molars with com- 

 pressed, outstanding parastyles and mesostyles Poebrodon 



2. Pi caniniform. Lower canine similar to incisors. 



a. Upper molars with prominent parastyle and ribs, but no mesostyle. 

 P' and P^ without accessory cusps. P4 with metaconid and simple 



talonid basin Hypertragulinae 



( I ) Posterior crest of protocone of upper molars directed toward met- 

 aconule. Anterior crest of hypoconid of lower molars directed 

 toward p>osterior crest of protoconid so as to leave a small 

 median pocket or basin between the crest of the hypoconid and 



the lingual wall of the tooth Simimeryx 



b. Upper molars with prominent parastyle and mesostyle, and ribs 

 prominent (early) to weak (later). Posterior crest of protocone 



