404 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



than in D. Tiyognathus; (c) the external cingula of 

 the molar teeth are a shade more prominent; [d) the 

 protoconule and metaconule have nearly vanished, al- 

 though inconspicuous vestiges still persist. 



The faint rudiments of the tetartocone folds of the 

 premolars are less marked than in certain specimens 

 of M. petersoni. The ectolophs of the superior 

 premolars are readily distinguished from those of 

 M. manteoceras by the flattening of the tritocones. 

 The ectoloph of p^ is simple and sharply convex. 

 That of p- consists of a prominent protocone convexity 

 which spreads downward into a broad cingulum bound- 

 ing the base of the tritocone (the same region in 

 D. Jiyognathus is strongly constricted); the tritocone 

 ectoloph is nearly flat or very slightly convex. In 

 p' the protocone ectoloph is a convex ridge spreading 

 toward the base into a cingulum, while the tritocone 



ectoloph is very gently convex but without a rib. 

 P* has the convexity opposite the apex of the proto- 

 cone, while the outer face of the tritocone is slightly 

 convex and the basal cingulum is nearly continuous 

 across the ectoloph. The above-mentioned features 

 enable us to distinguish the upper premolars from 

 those of Manteoceras and of both D. intermedius 

 and D. Tiyognathus. 



Summary. — In the lectotype lower jaw of D. 

 rallidens the premolars are decidedly more primitive 

 than in D. hyognathus. In the paratype upper 

 dentition of D. vallidens the premolars are somewhat 

 more primitive than in D. hyognathus. It is thus 

 not certain that the lectotype and paratype belong to 

 precisely the same stage of evolution; but, on the 

 other hand, there is no evidence that they are specifi- 

 cally distinct. 



Comparative measurements, in millimeters, showing progressive proportions of skull and teeth of Dolichorhinus 



Premaxillaries to 



condyles 



End of nasals to 

 middle top of occi- 

 put 



Face, anteroposterior. 

 Cranium, anteropos- 

 terior 



Transverse zygomata 



Pi-m3 



P2-m3 



P2-p< 



Mi-m3 



P', ap. by tr 



P^, ap. by tr 



M', ap. by tr 



M2, ap. by tr 



M3, ap. by tr 



D. supe- 

 rior, 

 Field 

 Mus. 

 12188 

 (type) 



224 

 184 



I), intermedius 



Am. 

 Mus. 

 1837 

 (type) 



475 

 230 



236 



'190 



179 



165 



57 

 109 



Am. 

 Mus. 

 2001 



475 

 241 



248 

 '■223 

 177 

 164 

 57 

 105 

 12X10 

 19X2120X25 

 31X32| 30X? 



39X38 



36X37 39X39 



D. val- 

 lidens, 



Am. 



Mus. 



5097 



D. het- 

 erodon, 

 Carne- 

 gie 

 Mus. 

 2340 

 (type) 



487 



492 



245 



240 



189 

 173 



114 



.22X25 

 .133X32 

 .|42X4I 

 .[39X38 



D.flu- 



minalis. 

 Field 

 Mus. 

 12205 

 (type) 



520 



233 

 171 



105 



D."lon 

 giceps," 



Carne- 

 gie 



Mus. 



2347 



(type) 



590 

 °270 



-285 



-264 



197 



178 



60 



115 



15X10 



D.lon- 

 giceps?. 



Am. 



Mus. 



1852 



573 

 270 



283 



230 



202 



■185 



62 



118 



15X11 



21X2920X26 

 35X?36X33 



39X40J41X39 

 39X?i40X37 



D. hyognathus 



Am. 

 Mus. 

 13164 



580 

 '290 



250 



205 



186 



65 



119 



18X11 



23X29 



36X33 



43X42; 



42X42 



Am. 

 Mus. 

 1850 



593 

 '260 



320 



208 



185 



61 



120 



16X9 



22X25 



36X30 



41X38 



43X35 



Am. 

 Mus, 

 1851 



550 



570 

 280 



288 



»240 



208 



187 



65 



122 



15X10 



23X27 



34X34 



43X43 



45X? 



Am. 

 Mus. 

 1845 



290 

 215 



'565 



Field 

 Mus. 

 12167 

 (D. 

 'cornu- 

 tus") 



310 



131 



25X30|. 



35X33|. 

 47X41. 

 47X41. 



285 



214 



135 



575 

 270 



298 



231 



206 



186 



62 



123 



15X10 



22X27 



35X33 



42X40 



44X39 



' Estimated. 



12188. Uinta B 1. 



1837. Female. Uinta B 2. 



2001. Uinta B 2. 



5097. Washakie B. 



2340. Uinta B 2 (upper level). 



12205. Uinta B 2. 



2347. Uinta B 2 (low level). 



1852. Female. Uinta B 2. 



13164. Washakie B 2. 



1850. Male. Uinta B 2. 



1851. Female. Uinta B 2 (type of 



Telmatotherium cornutum) . 

 1845. Uinta B 2. 

 1848. Uinta B 2. 

 12167. Uinta B 2. 



The above table shows the dolichocephalic propor- 

 tions of the cranium proper and of the true molars 

 and the smaller dimensions of D. intermedius and the 

 intermediate proportions of the type of D. heterodon. 

 The type of D. longiceps and the type of D. "cornutus" 

 agree well in size with the skulls of D. hyognathus. 

 The well-preserved skull from the Washakie Basin 

 (Am. Mus. 13164), which is referred to D. hyognathus, 



does not differ greatly in measurements from the type 

 of Dolichorhinus "cornutus" and the other Uinta B 

 specimens. The skulls of D. hyognathus, from Uinta 

 B, show a considerable difference in size, ranging from 

 the relatively small skull No. 1852 to the very large 

 skull No. 1845. 



Measurements of the lower jaws of these species are 

 given on page 416. 



