426 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



4. In the side view the form of the lambdoidal 

 ridges of the occiput is not dissimilar to that of Meta- 

 7-hinus ; however, these ridges do not unite above into 

 a narrow median crest as they do in MetarTiinus 

 fluviatilis but form a flattened vertex which suggests 

 that of Dolichorhinus intermedins. Possibly the median 

 crest of the adult M. fluviatilis may be derived by the 



Figure 359. — Lower jaw of Metarhinus? (Rhadinorhinus?) sp. 



One-fourth natural size. Am. Mus. 1859; White River, Uinta Basin, Utah, 



Uinta B 1. 



upgrowth of these lambdoidal ridges toward the mid- 

 line. At any rate the form of occiput seen in Hetero- 

 titanops is not seen elsewhere outside the subfamily 

 Dolichorhininae. In brief the animal named Eeteroti- 

 tanops parvus may provisionally be regarded as the 

 young of Metarhinus fluviatilis. 



The postcranial skeleton has been well described by 

 Peterson and is chiefly interesting as illustrating the 

 highly progressive or caenogenetic character of the 

 slceleton, which foreshadows the adult in the expansion 

 of the scapula, of the proximal end of the humerus, and 

 of the ilia, as well as in the great relative size of the 

 thorax and in the general proportions of the limb 



bones. 



Metarhinus earlei Osborn 



Plates LXXVIII-LXXX; text figures 124, 219, 302, 358, 361, 

 407, 521, 522, 573-575, 577, 647, 745 



[For original description and type references see p. 183. For slseletal characters 

 see p. 644] 



Type locality and geologic horizon. — North side of 

 Haystack Mountain, Washakie Basin, Wyo.; Meta- 

 rhinus zone (Washakie B 1). Also abundant in Uinta 

 Basin, Utah, at the summit of the Metarhinus zone 

 (Uinta B 1), in the " Metarhinus sandstones" of Riggs. 



Specific characters. — Skull (Am. Mus. 13166, type), 

 length 393 millimeters, breadth 240, or 388:245, 

 or 405:255; cephalic index 60-63. Occipital condyles 

 narrow (78 mm.), premaxillary symphysis elongate, 

 nasals elongate, spreading distally, prominent in- 

 fraorbital shelf . Type p'-m', 167 millimeters. Molar 

 series broad and low crowned, no hypocone on m^; 

 canines slender, diastema short. 



This animal is readily distinguished from M. 

 fluviatilis by its superior size and by the lesser prom- 

 inence of the orbits. 



Geologic distribution and materials. — The type of 

 this species is a skull (Am. Mus. 13166), fortunately 

 discovered by the American Museum expedition of 

 1906 in Washakie B 1. The nasals and the naso- 

 frontal horn region of the type are broken away. 

 A jaw belonging to another individual (Am. Mus. 

 13179) was also found in Washakie B 1 and agrees 

 approximately in measurement with this skull. It 

 may prove to belong to the same species. 



In the Riggs collection of the Field Museum there 

 are two skulls (Nos. 12169 and 12187), also two lower 

 jaws (Nos. 12178 and 12189). These four specimens 

 are recorded from the uppermost " Metarhinus sand- 

 stones, " or the Metarhinus zone (Uinta B 1). 



Skull. — The first feature of note in the type skull is 

 the mesaticephalic proportions, the measurement being 

 240 millimeters across the zygomata and 393 from 

 the condyles to the symphysis — that is, the width 

 is a little less than two-thirds the length, whereas in 

 Mesatirhinus petersoni skulls the width is only a 

 trifle more than one-half the length. Correlated 

 with this feature is the relative narrowness of the 

 occipital condyles (78 mm.). The occipital region is 

 also distinctive because of a deep pit on the upper 

 part of the occiput and a pair of hooldike processes 

 ttu-ning inward on the borders of the occipital crest 

 (fig. 361); these falciform, incurved, overhanging 

 borders are quite distinctive. The sagittal crest is 

 short. The infraorbital shelf is prominent but 



Figure 360.- 



-Skull and deciduous teeth of type of 

 Heieroiiianops parvus 



One-half natural size. Alter Peterson. Carnegie Mus. 2909 (type), White 

 River, Uinta Basin, Utah, Uinta B 1. Possibly a young Metarhinus. 

 A, Skull; B, right upper deciduous molars (dp^, dp^ dp^); the anterior 

 tooth is probably the permanent p'; C, left lower deciduous molar (dp(). 



slender. There is no hypocone on m^. We are espe- 

 cially struck by the prolongation of the premaxillary 

 symphysis, as illustrated in Figure 361, and the resem- 

 blance to Dolichorhinus. The well-preserved basi- 

 cranial region, which is also of mesaticephalic character, 

 indicates the affinities of this species to Mesatirhinus 

 megarhinus and more remotely to M. petersoni. 



