BIG BADLANDS OF SOUTFI DAKOTA. 483 



furrows running lengthwise, both front and rear. The enamel is 

 rugose, the crown slightly incurved and the tooth almost in contact 

 with p4. 



P4 has two high cones, of which the deuterocone is slightly the 

 higher, and measures 37 mm. anteroposteriorly (externally) by 36 

 transversely. The crown is much wider externally because of the 

 strong indentation anteriorly as in Archccotherium. The outer and 

 back sides are square, the inner side rounded and the front broadly 

 notched. The cingulum is very strong posteriorly with minor mam- 

 millations. Elsewhere it is less strong and is continuous about the 

 crown except for a small space on the inner side. 



The part of the skull retaining these teeth (Fig. 11) has been 

 laterally crushed and drawn out to some extent, so that correspond- 

 ing diastemata on opposite sides are not always of the same length. 

 The infraorbital foramen is above and in line with the front edge 

 of pj. 



In the lower jaw the incisors have already been described and 

 illustrated in discussing the root-digging habits of the animal. The 

 canines are strongly curved outward and backward and each has a 

 deep groove at the base of the enamel posteriorly, over which the 

 thin edge of the alveolus has partly grown. 



Pi is small, double-rooted and laterally compressed, with sharp 

 cutting edges front and rear and a backward and inwardly curved 

 crown. It is 7 mm. back of the canine and in line with it, and out 

 of line with all the other teeth. It measures, on the alveolar border, 

 31.5 by 19 mm., narrowing posteriorly. There is a 25 mm. diastema 

 back of it. On the right side its posterior edge is notched by root 



digging (Fig. 13). 



P2 is rather small and double-rooted, 39 mm. anteroposteriorly 

 on the alveolar border by 21 transversely, with a very high, sharp- 

 pointed crown curving slightly backward and inward and with a 

 sharp edge posteriorly. Enamel finely rugose. Diastema back of 

 this tooth 20-23 mm. long. 



P3 is a great tooth 54^/2 mm. anteroposteriorly on the alveolar 

 border by 28 at the widest part of the crown and rises 84 mm. above 

 the alveolar border in front. It is a single cone with no heel, some- 

 what recurved, with a strong posterior cutting edge and moderate 



PROC. AMER. PHIL. SOC, VOL. LX, FF, MARCH I7, I922. 



