Plate XLI 



Comparative Series: Occlusal Relations of the Upper and Lower Cheek Teeth 



Lingual aspect. 



All figures three times naliiial size. 



1. Pelycodus trigonudiis. Anier. Mus. No. 15017. Lower Eocene, Gray Bull Beds, Bighorn Basin, Wyoming. 



2. Notharctus crassuis. Amer. Mus. No. 11982. Upper Bridger, Henry's Fork, Wyoming. 



3. Adapts parisiensis. Amer. Mus. No. 10007 (mandible) and 10005 (second and third upper molar). 



