410 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Materials.— 1:^0 other Eocene titanothere is repre- 

 sented by so rich cranial material as this species. 

 The numerous skulls and jaws, although uniformly 

 recorded from the DolichorTiinus (cornutus) Tiyognathus 

 zone (Uinta B 2 and Washakie B 2), were undoubtedly 



Figure 345. — Hyoid apparatus of Dolichorhinus longiceps? 

 (1, 3) compared with that of a modern tapir, Tapirus ter- 

 restris (2) 



One-haU natural size. After Peterson. The two upper figures show a front view, 

 the three lower a side view. This almost unique fossil belongs with the skull and 

 jaws previously figured (fig. 34-1) and other bones comprising the specimen Car- 

 negie Mus. 2865. bh, Basihyal; th, thyrohyal; ch, ceratohyal; eh, epihyal; sh, 

 stylohyal. Compare the hyoid bones of Brontops sp. (Am. Mus. 518, fig. 425). 



found at somewhat different levels and may represent 

 different stages of mutative progression, although it 

 seems impracticable to separate them into species. 

 These crania are enumerated below. 



Washakie B 2: 



Princeton Mus. 10273, type of D. hyognaihus; jaw of an 



aged animal. 

 Am. Mus. 13164, skull and jaws of a young adult female; 



m' slightly worn, associated with parts of skeleton, fore 



limb, and parts of vertebrae. 



Uinta B 2: 



Am. Mus. 1850, skull of a young adult male; m^ just appear- 

 ing. 



Am. Mus. 1845, skull of a young adult; m^ in place but 

 unworn. 



Am. Mus. 1851, skull (type of Telmatotherium cornutum) 

 of aged female; m^ well worn. 



Am. Mus. 1852, skull of young female; m^ slightly worn. 



Am. Mus. 1848, very old skull; m^ greatly worn, sex inde- 

 terminate. 



Am. Mus. 1843, anterior part of skuU of large size, asso- 

 ciated with complete backbone and humerus. 



Am. Mus. 1849, parts of skull and fragments of skeleton 

 doubtfully recorded as of base of Uinta B 2. 



Field Mus. "l2167, skull from Uinta B (1 or 2). 



Jaws. — Besides the type of D. hyognaihus from 

 Washakie B 2, we have the jaws Am. Mus. 13164, 

 associated with a skull. Also from Uinta B 2 we have 

 thirteen jaws more or less completely preserved, in- 

 cluding Am. Mus. 1834, 1836, 1840, 1852, 1854, 1855, 

 1856, 1857, 1858, 1941, 2008. 



STcull. — The afiinities of the skull of these animals 

 to that of Mesatirhinus petersoni are apparent in 

 many details of structure, but, as above noted, there is 

 a very marked progressive advance, which is bridged 

 over partly by the intermediate stages of D. inter- 

 medius and D. longiceps. The affinity to M. ( = Doli- 

 chorhinus) superior is still closer. The full descrip- 

 tion which follows is based principally on the female 

 skull Am. Mus. 1851 (type of Telmatotherium cornu- 

 tum) and the superb skull and jaws, also of a female 

 (Am. Mus. 13164), from Washakie B 2. 



In the superior aspect (fig. 346) we are immediately 

 struck by the extraordinary elongation of the nasals, 

 which extend behind the line between the orbits and 

 occupy a little less than one-half of the entire length of 

 the skull. The longitudinal suture persists between 

 the nasals and is traceable a short distance back 

 between the frontals. These bones expand to 129 

 millimeters immediately above the orbits and are 

 convex both anteroposteriorly and transversely; the 

 line of junction between the frontals and parietals is 

 obliterated. The vertex is here arched both trans- 

 versely and longitudinally. The supratemporal ridges, 

 now wholly lateral in position, follow the superior 

 border of the supratemporal fossa; the top of the 

 cranium is expanded slightly to 108 millimeters and 

 then contracts to 62 millimeters just in front of the 

 junction with the occipitals. This flattened arching 

 and spreading of the vertex of the skull naturally differs 

 both according to age or growth and the progressive 

 stage of evolution which the skull represents. The 

 superior view also displays the comparatively long 

 and slender zygomatic arches, which reach a maximum 

 width of 245 millimeters and an average width of 231, 

 as compared with 550, the total length of the skull. 



Horns. — The nasals diverge suddenly into the 

 osseous horns, which lie directly above the orbits, 

 whereas in M. manteoceras the horns lie in front of the 

 orbits; they present an outward-directed elongate- 

 oval convexity, to the posterolateral portion of which 

 only the frontals contribute. On the vertex between 



