Cope.] "by) [Feb. 10, 



equaling the larger individuals of Oreodon culbertsoni. The molar teeth 

 are, however, relatively larger than in that animal and in the species of 

 Eucrotaphus, and the anterior premolars and incisors smaller and more 

 crowded. The last two premolars are in line, but the second premolar is 

 set obliquely in the jaw so as to overlap the first premolar by the whole of 

 its anterior root, and the third premolar by half of its posterior root. The 

 anterior root is interior, the posterior exterior. The first premolar has a 

 robust root with round section, The crown is but little expanded at the 

 posterior base ; anterior part and apex lost. The alveolus of the canine 

 diverges somewhat outward. The symphyseal suture is short and rather 

 deep. Its posterior edge is below the posterior quarter of the third pre- 

 molar. 



The outline of the jaw is nearly vertical behind, with rounded angle, 

 and abrupt excavation below the condyle. Its edge is beveled outwards 

 except opposite the grinding edge of the last molar where there is a thick- 

 ening on the external side. The masseteric fossa is well impressed, but 

 rather small, descending only to the line mentioned. On the contrary the 

 fossa of the internal pterygoid muscle occupies the entire jaw behind the 

 line of the third molar, and is bounded posteriorly and at the angle, by an 

 incurved edge. Dental foramen opposite middle of last molar. Mental 

 foramen below posterior edge of second premolar. 



Measurements. M. 



Length of ramus at line of mental foramen 150 



" " molar series 096 



" " premolar series 042 



" " third premolar . . * 0125 



" fourth " 013 



Diameters m . jjj anteroposterior 0165 



I transverse 012 



Length of ra. iii 025 



Depth ramus at p-m. iii 080 



" " " m. iii, front 035 



In the Merychyus pariofjonvs Cope of the Deep River Ticholeptus bed, 

 the posterior part of the ramus is more expanded, and is perfectly 

 rounded, while the other dimensions are considerably smaller. 



From Cottonwood creek, Oregon ; J. L. Wortman. 



Hippotiieiutjm: rectidens, sp. nov. 



The probable Loup Fork Upper Miocene formation of Tehuichila, State 

 of Vera Cruz, Mexico, lias yielded a third species of three-toed horse, 

 which differs from any of those known to me "" I owe the superior molar 

 tooth on which the evidence depends, to my friend, Dr. Santiago Bemad, 

 to whom I am already indebted for the other species known to me, and 



♦See Proceedings American Phllosoph. Society, 1885, p. 150 (1886), for descrip- 

 tions <>( two species, Hippotherium peninsvlatum and Protohippus castilli. 



