BIG BADLANDS OF SOUTH DAKOTA. 



477 



In No. 12529, found last summer by Mr. Wanless in the clays of 

 the " turtle-oreodon layer " of the lower Oreodon beds in the valley 

 of Indian Creek, Pennington County, South Dakota, a young skull 



Fig. 7. Fig. 8. 



Fig. 7. Archaotherium mortoni Leidy. No. 12529. Portion of left jugal 

 seen from the outer side showing both the dependent and the posterior proc- 

 esses, one half the natural size. 



Fig. 8. Archaotherium mortoni Leidy. No. 11440. End of the dependent 

 process of the right jugal showing concavity of anterior margin and thicken- 

 ing of distal end, one half the natural size. 



with both milk and permanent premolars in place and the third 

 molar just appearing, the process is slender and thin, 8 mm. in max- 

 imum thickness in the middle and about two millimeters thicker at 

 the distal end. Transversely, it is 41 mm. at the widest part. 



In the second specimen, No. 11440, from the lower Oreodon beds 

 at the head of Sand Creek, Nebraska, collected by Mr. J. W. Gidley 

 in 1896, the tip of the process on the right side seems to have been 

 injured during life, for the anterior margin is concave distally and 

 the process ends in an expanded area with a rugose flattened face 

 measuring 15 mm. vertically by 27 transversely. No comparison 

 can be made with the corresponding structure on the opposite side, 

 as this has been broken off. 



