EVOLUTION OF THE SKULL AND TEETH OF EOCENE TITANOTHERES 



Dolichorhinus vallidens (Cope) 



Plate LXXIV; text figures 95, 341, 353 

 [For original description and type references see p. 362] 



Geologic horizon. — Washakie Basin, Wyo., level 



401 



Washakie B. 



than in D. hyognathus; hypoconulid of m^ elongate; in 

 general more primitive than either D. intermedins or 

 D. hyognathus. 



As shown above, the imperfectly preserved upper 

 and lower jaws, the co types of Cope's original descrip- 

 tion, were not found together. Nevertheless it now 



FiGUBB 339. — Skulls showing progressive dolichocephaly in the Mesalirhinus-Dolichorhinus phylum 

 Side view. Ono-fourth natural size. A, Mesatirhinus petersoni, British Mus. (formerly Am. Mus. 1556), Big Bone Mountain, Henrys 

 Fork, Bridger Basin, Wyo., Bridger D; B, Dolichorhinus superior, Field Mus. 12188 (type), Uinta Basin, Utah, Uinta B 1; C, D. longiceps, 

 Carnegie Mus, 2347 (type), Uinta Basin, Uinta B 2; D, D. hyognathus, Am. Mus. 1851, White River, Uinta Basin, Uinta B 2. 



Specific characters. — P'-m^ 185 millimeters (esti- 

 mated); mj-m,,, 123; ectolophs of superior premolars 

 with a broad basal spreading of the protocone con- 

 vexities; tritocones more flattened than in D. inter- 

 medins; p^, p^ of same proportions asm D. hyognathus; 

 lower premolars less compressed and more primitive 



appears probable though not certain that the lectotype 

 lower jaw (Am. Mus. 5098) and at least one of the 

 original upper dentitions (Am. Mus. 5097) do pertain 

 to the same species. 



Doubtful reference. — The reference of these types to 

 Dolichorhinus is provisional; if the jaws are correctly 



