183 



[Cope. 



sub-round, and are anterior to the transverse line of the interior ones. 

 They do not join the hitter excepting after very considerable wear. The 

 external anterior cingular cusp is rather more prominent on the first than 

 on the second true molar. The fourth superior premolar has a well marked 

 external anterior cingular cusp, which is, however, low ; and there is no 

 ridge dividing the external faces of the external cusps. The single inner 

 cusp is connected with the two external by two ridges, which diverge as 

 they extend outwards. The anterior supports a tubercle close within the 

 anterior external. There are strong anterior and posterior basal cingula 

 and weak external and internal ones. 



The third inferior premolar has a compressed ridge on the heel. The 

 fourth premolar is like a true molar, with the anterior inner cusp well de- 

 veloped and elevated, and connected with the anterior and posterior ex- 

 ternal by oblique ridges. The inner posterior cusp is less conic in form 

 than in the true molars, and the entire crown is somewhat contracted 

 anteriorly. The true molars are characterized by the presence of a small 

 median tubercle on the posterior border. There is a low external basal 

 cingulum, which is wanting opposite the posterior cusp. Enamel generally 

 smooth. 



3Ieasurements. M. 



Length of superior true molar series 0310 



_. ^ . -M- TT f anteroposterior 0080 



Diameters of superior M. II -^ ^ „„nrT 



^ I transverse 0097 



^. „^ „^ r anteroposterior .0085 



Diameters oi F-m, iV < , naor 



\ transverse 008j> 



Length from inferior P-m. Ill to M. II inclusive 0290 



■r^ ^ -r^ TTT r anteroposterior 0080 



Diameters of P-m. IV , nrie^n 



{ transverse. . , 0050 



T^. ^ c • p ■ TIT TT r anteroposterior 0075 



Diameters of inferior M. II < ^ „ „^„ 



I transverse OObO 



Depth of ramus batweeu P-m. Ill and P-m. IV 0150 



As compared with the 0. cinctus* this species differs in its superior 

 dimensions. The anterior inner cusp of the inferior molars is probably 

 single, though the slightly worn condition of those teeth renders this 

 point a little uncertain. In 0. ductus some of them at least are double. 



This species was, to judge from the size of its teeth, about the size of a 

 red-fox. The specimens of it above described were found by Mr. J. L. 

 Wortman in the bad lands of the Big-Horn river, Wyoming. It is dedi- 

 cated to my friend, Henry L. Osborne, of Princeton College, New Jersey. 



Systemodost tapieinus Cope. American Naturalist, 1881, p. 1018. 



HyracotJierium tapirinum Cope. Systematic Catalogue of the Eocene 

 Vertebrata of New Mexico, 1875, p. 20. Report U. S. Geol. Surv. W. of 

 100th mer. Capt. G. M. Wheeler, iv. ii. p. 363. PI. Ixvi. figs. 13-16. 



This species was abundant in Wyoming during the Wasatch epoch, 

 jaws and teeth of more than twenty individuals having been brought by 



* Annual Eept. U. S. Geol. Survey Terrs. 1872, p. G07. 



