388 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Measurements oj Mesatirliinus megarhinus, M. petersoni, Dolichorhinus superior, and Metarhinus fluviatilis, in 



millimeters 



* Estimated. 



10008. Washakie Basin. 

 1514. Washak;ie A. 

 12202. Bridger C 5. 



1523. Bridger C or D. 

 1571. Washakie A. 

 1509. Bridger D. 



1556. Bridger D. 

 12184. Bridger D 3. 



12188. Uinta B 1. 

 1500. Uinta B 1. 



The figures show that M. petersoni, most specimens 

 of which are from the higher levels of Bridger D, is 

 considerably larger in all measurements than M. 

 megarJvinus. Both are much larger than the type of 

 Metarhinus fluviatilis from Uinta B 1. 



Mesatirhinus Junius (Leidy) 



Text figures 91, 325 

 [For original description and type references see p. 159] 



Type locality and geologic horizon. — The type lower 

 molar of M. Junius, according to Leidy's description, 

 was found near Fort Bridger, Wyo., at a geologic level 

 that Granger places in Bridger B. If this geologic 

 level is correct M. Junius is the oldest known species 

 in the Mesatirhinus phylum. Its geologic age must, 

 however, be regarded as indeterminate. 



Specifl.c characters. — A doubtfully referred specimen, 

 imperfectly known. M'-m^, 69 millimeters. A dimi- 

 nutive Mesatirhinus or Metarhinus. 



Materials. — The type specimen (Acad. Nat. Sci. 

 Philadelphia) is very fragmentary. The only other 

 material that may be referred even provisionally to 

 this species is a diminutive set of teeth, including 

 ml to m^ (Am. Mus. 12686), from level D 5 of the 

 Bridger. The teeth present generic resemblances to 

 those of Mesatirhinus megarhinus but are far smaller 

 than in any known upper Bridger, Washakie, or Uinta 

 titanothere, m'-m' measuring only 69 millimeters, as 

 against 85 in Metarhinus fluviatilis . The teeth are less 

 hypsodont than in allied species; m' is relatively very 

 small and m' very quadrate. A comparison of the 

 lower molar with the type ms of Palaeosyops Junius 

 Leidy leaves the specific identity doubtful. The com- 

 parative measurements are as follows: 



Mesatirhinus megarhinus (Earle) 



Plate LXXII; te.xt figures 106, 217, 324, 326, 328, 330, 331, 508, 

 510, 558, 560, 561, 685, 737 



[For original description and type references seep, 170. For slieletal ciiaracters see 

 p. 637] 



Type locality and geologic horizon. — Washakie Basin, 

 Wyo.; probably Washakie A. The species is also 

 recorded from Bridger Basin, Wyo., Uintatherium- 

 Manteoceras- Mesatirhinus zone, level Bridger C 

 ( = Washakie A). 



Specific characters. — P'-m^, 140-147 millimeters; 

 true molars, 77-83. Cephalic index, 56-59. Cranial 

 length, premaxillaries to condyles, 354 millimeters 

 (estimated); facial region rather short (about 170 

 mm.); faciocephalic inde-x 48 (estimated); occipital 

 condyles broad; premaxillary symphysis short; infra- 

 orbital shelf prominent. Tetartocones on p^, p* very 

 rudimentary. Nasofrontal horns incipient. 



Materials. — The type (Princeton Mus. 10008) is 

 badly preserved and unfortunately lacks the occipital 

 condyles, which appear to be relatively broader in 

 Mesatirhinus than in Dolichorhinus. The geologic 

 level of the type is not definitely recorded, but is 

 probably Washakie A. 



