192 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



The position of the posterior narial opening is the most distinc- 

 tive character, appearing much farther back in D. fluminalis 

 than in any other described species. The two forms agree more 

 closely in the tapering form of the nasals and in the narrow 

 recess separating them, from the maxillaries. 



Etymology. — fluminalis, pertaining to rivers; in 

 allusion to the habitat. 



Present determination. — A stage in the DolichorTiinus 

 phylum, not very clearly distinguished specifically 

 from other progressive stacc?. 



,to» 



Figure 140. — Type (holotype) skull of Dolichorhinus fluminalis 

 Field Mus. 12205. After Eiggs, ] 912. Side, top, and palatal views. About one-fifth natural size 



Rhadlnorhinus Riggs, 1912 



Cf. Rhadinorhinus, this monograph, page 430 



Original reference. — Field Mus. Nat. Hist. Pub. 159, 

 Geol. ser., vol. 4, No. 2, p. 36, June, 1912 (Riggs, 

 1912.1). 



Type species. — Rhadinorhinus ahbotti Riggs. 



Generic characters. — Riggs writes : 



Titanotheres with slender skulls, nasals deeply recessed later- 

 ally and tapering, molars long-crowned, p-- ^- * subrectangular, 

 a wide median area between the incisors, no infra-orbital 

 process. The name Rhadinorhinus alludes to the tapering 

 nasals which characterize this genus. 



Etymology. — pa8iv6s, slender; pis, nose. 

 Present determination. — Probably a valid stage, an 

 extreme offshoot of the Metarhinus phylum. (See 

 p. 17, fig. 15.) 



Rhadinorinus abbotti Riggs, 1912 

 Cf. Rhadinorhinus ahbotti, tliis monograph, page 430 



Original reference. — Field Mus. Nat. Hist. Pub. 159, 

 Geol. ser., vol. 4, No. 2, p. 36, pi. 11, figs. 2, 3, June, 

 1912 (Riggs, 1912.1). 



Type locality and geologic horizon. — 

 Northeastern Utah; "upper Meta- 

 rhinus beds," center of Metarhinus 

 zone (Uinta B 1). 



Holotype. — A fine skull (Field Mus. 

 12179). (See fig. 141.) 



Specific characters. — Riggs says: 



Length of skull 435 millimeters, molar- 

 premolar series 168 millimeters, nasals shorter 

 than premaxillaries, thickened at suture, and 

 tapering toward a terminal rugosity. Arches 

 slender, posterior nares open opposite middle 

 of m2. Sagittal crest long and narrow. 

 Hypocone of m' vestigial, diastema short. 



Etymology. — Named in honor of 

 Mr. J. B. Abbott, of the Field 

 Museum of Natural History. 



Present determination. — A valid spe- 

 cific stage. 



Eotitanops gregoryi Osborn, 1913 



Cf. Eotitanops gregoryi, this monograph, 

 page 291 



Original reference. — Am. Mus. Nat. 

 Hist. Bull., vol. 32, p. 407, fig. 1; 

 p. 411, fig. 4B, September 2, 1913 

 (Osborn, 1913.400). 



Type locality and geologic horizon. — 

 Type from Wind River Basin, Wyo., 

 100 feet above Alkah Creek "red 

 stratum . ' ' Lamhdotherium-Eotitanops- 

 Coryphodon zone (Wind River B, 

 "Lost Cabin"). 



Type. — An incomplete lower jaw, 



containing the right lower premolar- 



molar series (pa-ms), also fragments 



of left maxilla containing m", m^ (Am. Mus. 14889). 



(See fig. 142.) 



Specific characters. — Osborn writes: 



Of inferior size. P2-m3, 78.4 millimeters; mi_3, 49; P2-3 

 with the internal cusps, paraconid and metaoonid, consisting 

 of rectigradations of most rudimentary stage; hypoconulid of 

 ms very small; m^ with a single internal cone, no hypocone. 



This very sharply defined species may represent a 

 persistent primitive stage, because its recorded 

 (Granger) geologic level, 100 feet above the Alkali 

 Creek "red stratum," is higher than that of the 



