660 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



made, presents characters not unlike those in the Princeton 

 specimen referred to Diplacodon elatus (see above) . However, in 

 the specimen under description (possibly a female) the coracoid 

 is seen to be relatively smaller than in the latter. The groove 

 between the base of the coracoid and the border of the glenoid 

 cavity is larger in proportion than in Menodus, and the excava- 

 tion on the coracoid border, immediately above the coracoid, 

 has a less abrupt curvature. This is due to the smaller develop- 

 ment of this angle in Eoiitanotherium. The coracoid border is 

 otherwise quite straight as in Menodus. The superior portion 

 of the glenoid border is broken off, but in the region of the break 

 there is a similar broad extent of the superior portion of the 

 blade. The spine is damaged, but it was apparently overhang- 

 ing like that in Diplacodon described by Osborn, and thus less 

 extended over the postscapular fossa than in Menodus. 



In comparing the humerus of the present form with that of 

 Brontops validus, the difference most noticeable is the relative 

 robustness and the length. In the Oligocene form the bone is 

 short and very heavy, while in the present genus the bone is 

 longer in proportion and also lighter. Superiorly the greater 

 tuberosity extends higher above the head than in Menodus but is 

 not so robust, the proximal end as a whole being more delicately 

 proportioned. The bicipital groove is deep and well defined, as 

 in the Oligocene genus. On the other hand the deltoid ridge, 

 though very prominent, does not terminate in the heavy 

 recurved process as in B. validus but descends much more 

 gently toward the supratrochlear fossa. Distally there is less 

 variation between the two forms here compared. The anconeal 

 fossa in the species under description is relatively broader, and 

 the supinator ridge is less rugose. The trochlea is slightly 

 deeper but not more obliciue than in B. validus. 



The humerus as described and figured by Osborn holds an 

 intermediate position between the Oligocene genus and the 

 present form. This is especially shown in the development of 

 the deltoid ridge, which in the Princeton specimen is consider- 

 ably more developed than in the genus under description. 



Measurements of humerus of Eoiitanotherium, in millimeters 



" The shafts of the two bones are more or less crushed, and the measurement is 

 only approximately correct. 



Both radii and ulnae are represented in No. 2860. A third 

 radius was also found in the same sandstone ledge in close 

 proximity to the spot where Nos. 2858 and 2859 were found. 



The radius and ulna are long and relatively slender when 

 compared with those of the Princeton specimen of Diplacodon 

 and the Ohgocene genus B. validus. Thus the forearm of the 

 new genus is actually a little longer than in Diplacodon and is 

 very nearly as long as that of B. validus, notwithstanding the 

 much smaller size of the Uinta form of which we are speaking. 

 Another striking difference between the forms here compared is 

 the lateral expansion of the pro.ximal and distal ends of the 

 radius. In the Oligocene form the shaft of the radius is more 

 rounded in the middle region, while more proximally and distally 

 a sudden expansion takes place, which is also well displayed in 

 the Uinta specimen described and illustrated by Scott and 

 Osborn. In Eoiitanotherium osborni the shaft is flatter, more 

 uniform throughout, and the proximal and distal ends compara- 

 tively little expanded. 



The proportions of the ulna conform to the radius, and it is 

 consequently slenderer and proportionally longer than in 

 Diplacodon and Menodus. In detail the bone is otherwise quite 

 similar to that in the two latter genera, including the well- 

 defined tendinal groove on the anterior superior angle of the 

 olecranon process so characteristic of the ulna of Brontops 

 validus, but apparently less developed in the Princeton speci- 

 men, judging from the illustration (PI. IX, figs. 10-10 '^). 



Measurements of No. 2862 



Millimeters 



Radius, greatest length 380 



Radius, transverse diameter at middle of shaft 40 



Radius, transverse diameter of head 78 



Radius, transverse diameter of distal end 77 



Ulna, length of olecranon process 100 



The forefoot of No. 2860 is represented by the scaphoid, pisi- 

 form, trapezoid, Mtc II, IV, and V, and one or two phalanges. 

 No. 2859 has also Mtc IV and V represented. 



As might be anticipated from the description of the limb, it 

 is found that the foot is higher than in B. validus of the Oligo- 

 cene. Thus the scaphoid is higher in i)roportion and narrower 

 than in the latter species but is of considerable fore-and-aft 

 diameter. In detail there are only such differences as one might 

 expect from the general outlines described — that is, the different 

 articulating surfaces of the distal face are narrow and long, 

 while the articulation for the radius is less concave antero- 

 posteriorly than in the Oligocene form. The pisiform has a 

 similar long attenuated shaft terminating in an obtuse tuberosity 

 of considerable vertical diameter but transversely rather thin. 

 Besides the greater height of the trapezoid, the small posterior 

 superior facet for the magnum, which is characteristic of 

 Menodus, is practically wanting in the present form. Judging 

 from the facet on the posteroradial angle there is present in the 

 new Uinta genus a trapezium of considerably larger size. 



Mtc II is long, quite broad, but of small anteroposterior diam- 

 eter, which is in part due to crushing. The proximal end is 

 partly broken off, so that the different facets can not be accu- 

 rately compared. The shaft is of quite uniform width until the 

 distal articulating surface is reached, where there is on the 

 radial face a sudden expansion. This character is less apparent 

 in the Oligocene forms and also apparently less than in the 

 metacarpus of the Princeton specimen from the Uinta, as figured 

 by Scott and Osborn. Mtc IV is, as stated, represented by 

 fragments in both type and paratype and displays no features 

 of especial importance. 



Mtc V is longer and slenderer than the same element in B. 

 validus and that referred to Diplacodon (PI. IX, fig. 13). Prox- 

 imally and distally the bone is expanded much as in Menodus, 

 and the shaft, though relatively longer, is of a similar cylindroid 

 character. The facet for Mtc IV is located more laterally than 

 in the Oligocene genus, and the dorsal and ulnar faces are less 

 deeply grooved for muscular attachments. Near the distal end 

 is a flange on the postero-ulnar angle, which is similar to that 

 already described on Mtc II and is not generally present in the 

 Ohgocene titanotheres. 



There is apparently more inequality in size between Mtc II 

 and Mtc V than represented in the figure of the manus of 

 Diplacodon by Scott and Osborn. This is very probably due, 

 to some extent, to the crushing of Mtc II of the specimen in 

 the Carnegie Museum. In the specimen at Princeton the com- 

 plete length of Mtc V is apparently represented. Its measure- 

 ments appear to be only about 13 millimeters longer though 

 nearly one-third broader than that of the specimen before us. 



The phalanges are short, broad, and in every respect titano- 

 theroid. 



