DISCOVERY OF THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



183 



Metarhinus Osborn, 1908 



Cf. Metarhinus Osborn, this monograph, page 420 



Original reference. — Am. Mus. Nat. Hist. Bull., vol. 

 24, p. 609, 1908 (Osborn, 1908.318). 



Type species and geologic liorizon. — Metarhinus flu- 

 viatilis Osborn. Washakie Basin, Wyo., level Washa- 

 kie B; Uinta Basin, Utah, levels Uinta B 1 and B 2. 



Specific charac- 

 t er s . — Osborn 

 writes : 



Small tltanotheres 

 (skull length 355 to 440 

 mm.), persistently mes- 

 aticephalic. Narrow, 

 abbreviated preorbital 

 region, premaxillary 

 symphysis greatly 

 elongated, and anterior 

 narial openings deeply 

 recessed in side view. 

 Infraorbital shelf pres- 

 ent, or wanting (M. 

 diploconus) ; occipital 

 condyles narrow. 

 Grinding teeth sub- 

 hypsodont; premolars 

 progressive; hypoco- 

 nulid of ms small, 

 conic. 



Etymology. — iiera, 

 after; rJiinus (that 

 i s , MesatirMnus) . 

 "The name alludes 

 to the somewhat 

 later geological ap- 

 pearance of this 

 genus as compared with MesatirMnus." (Osborn.) 

 Present determination. — The genus is valid. (See 



p. 420.) 



Metarhinus fluviatilis Osborn, 1908 



Cf. Metarhinus fluviatilis Osborn, this monograph, page 421 

 Original reference. — Am. Mus. Nat. Hist. Bull., vol. 

 24, p. 609, fig. 13, 1908 (Osborn, 1908.318). 



Figure 122. — Type (holotype) skull 

 of MesatirMnus petersoni 



Top view. Am. Mus. 12184. After Osborn, 1908. 

 One-fourth natural size. 



Figure 123. — Type (holotype) skull of Metarhinus fluviatilis 



Lett side. Nasals broken off. 



Am. Mus. 1500. 

 natural size. 



After Osborn, 1908. One-fourth 



Type locality and geologic liorizon. — Uinta Basin, 

 Utah; Metarhinus zone (Uinta B 1). 



Holotype. — A skull (Am. Mus. 1500) discovered by 

 the American Museum expedition of 1894 in horizon 

 B 1 of the Uinta Basin. (See fig. 123.) 



Specific characters. — Osborn writes: 



Pm'-m^ — 144 millimeters. A relatively short (355 mm., 

 estimated), broad (200 mm., estimated) skull. Eye sockets 

 small and very prominent. Premaxillary symphysis elongate, 

 grinding teeth subhypsodont, m' with a cingulum-hypocone in 

 the type. 



Etymology. — fluviatilis, fluviatile. "The name is 

 given in allusion to the possibly river-living or am- 

 phibious habits of the animal." (Osborn.) 



Present determination. — The species and the generic 

 reference are valid. For fuller specific distinctions 

 see page 421. 



Metarhinus earlei Osborn, 1908 



Cf. Metarhinus earlei Osborn, this monograph, page 426 



Original reference. — Am. Mus. Nat. Hist. Bull., vol. 

 24, p. 610, fig. 14, 1908 (Osborn, 1908.318.) 



Figure 124. — Type (holotype) .skull of 

 Metarhinus earlei 



Top view. Am. Mus. 13166. After Osborn, 1908. 

 One-fourth natural size. 



Type locality and geologic horizon. — North side of 

 Haystack Mountain, Washakie Basin, Wyo.; Meta- 

 rhinus zone (Washakie B 1 ) . 



Type. — A skull (Am. Mus. 13166) lacking the nasals, 

 American Museum expedition of 1906. (See fig. 124.) 



Specific characters. — Osborn writes: 



Pmi-ni' = 167 millimeters. Skull proportions, length 380, 

 breadth 230. Narrow occipital condyles. Extremely elongate 

 premaxillar}' symphysis. A short sagittal crest. No hypocone 

 on m^. 



This animal is readily distinguished from M. diploconus by 

 (1) the infraorbital shelf of the malars; (2) the elongate premaxil- 



