Measu rements. 



Specimen No. I was found at Cottonwood Creek, and 

 specimen No. 2 at Henry's Fork, Wyoming. 



HYOPSODUS, Leidy. 



Pr. Ac. Nat. Sc., 1870, p. no. 



Lower teeth : I. 3, C. i, Pm. 4, M. 3, in uninterrupted suc- 

 cession. Last molar has cusps in opposing" pairs ; the antero- 

 internal cusp on all the molars is single ; the last molar has a 

 heel, and the last premolar has an inner cusp. The true molar 

 cusps are all high and simple. 



HYOPSODUS PAULUS, Leidy. 



Loc. cit., p. no. 



This is one of the most common fossils found in the 

 Bridger Basin. We have numerous specimens, chiefly from 

 Henry's Fork, exhibiting a large range of individual and 

 sexual variation. As Dr. Leidy has already pointed out, the 

 strength and depth of the lower jaw is extremely variable, in- 

 creasing with the age of the animal ; so that the most worn 

 teeth are associated with the deepest jaws. 



* In measurements of teeth we use the word length to mean antero-posterior 

 diameter, and width to mean transverse diameter. 



