674 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



the proximal humeral facet; the presence of a promi- 

 nent rugosity for the insertion of the brachialis anticus 

 near the middle of the shaft; a deep median groove 

 180 millimeters below this rugosity for the common 

 extensor tendon; and a larger transverse diameter of 

 midshaft (72 mm.) as compared with the anteropos- 

 terior diameter (65 mm.)- 



The ulna is highly characteristic, measuring 600 

 millimeters over all. It is distinguished by the bifid, 

 prominent and deeply cleft olecranon; the concave 

 anterior surface of the shaft with very rugose inter- 

 nal and external borders.; and the reduced inferior 

 extremity. 



The manus (fig. 609) is highly characteristic of this 

 specimen and may be readily recognized by its breadth 



its width is 89 millimeters, its vertical anterior meas- 

 urement 54. The lunar is broad and depressed, with 

 a much broader magnum facet than in B. robustus; 

 its width is 90 millimeters, vertical depth (anterior) 

 59; it also rests widely upon the unciform. The 

 cuneiform is characterized by a broad external 

 tuberosity for muscular attachment. Width 64 mil- 

 limeters,, vertical height 47. The trapezoid measures, 

 scaphoid facet, anteroposterior 74 millimeters, vertical 

 33. The magnum (tr. 76, vert. 47) is the most highly 

 characteristic element, being readily distinguished 

 from that of either Menodus or Brontops rohustus 

 (type) by (1) its vertical wedgelike extension upward 

 between the scaphoid and lunar, (2) its exceptionally 

 large size and breadth, and (3) its narrow contact with 



Figure 609. — Manus of Brontops? sp. and Brontops disparf 



A, Am. Mus. 518, a mounted skeleton referred to Brontopsf; B, Carnegie Mus. 92, a mounted skeleton referred to Brontops dispar? 



are somewhat distorted by crushing. One-fourth natural size. 



The carpals of this specimen 



and massive proportions; the peculiar, irregular form 

 of the magnum, which is unlike that of either Menodus 

 or Brontops rohustus (type); the comparatively 

 broad and distally spreading terminal phalanges; and 

 the secondary carpal displacement, as shown in the 

 very broad lunar-magnum facet and the relatively 

 small size of the lunar-unciform facet. The propor- 

 tions are shown by the following measurements: 

 Width of proximal carpals (across facets), 207 milli- 

 meters; height of Mtc III, 218. These measurements 

 indicate that the manus is relatively broader, or has 

 less vertical depth, than that of the type of Brontops 

 robustus. 



The carpus, considered in detail and compared 

 especially with the carpus of Brontops robustus (PI. 

 CCXXVIII), shows these principal features: The 

 scaphoid has a broader displacement on the magnum; 



the unciform coi'related with the marked spreading 

 of the proximal end of Mtc III. The unciform has a 

 less transverse extent as seen from in front than in 

 either Menodus or Brontops robustus, correlated with 

 the less extreme displacement of the proximal carpals. 



The metacarpals exhibit the following linear meas- 

 urements: Mtc II, 212 millimeters; Mtc III, 218; Mtc 

 IV, 204. They are larger and somewhat more mas- 

 sive throughout than in Brontops robustus. A striking 

 feature is the great proximal width of Mtc III and 

 its elongate upward extension against the unciform 

 between the magnum and Mtc IV; this process is 

 much longer than in Menodus or in Brontops robustus 

 type. 



The terminal phalanges are highly distinctive, 

 being double the size of those of Menodus and much 

 larger than those of Brontops robustus; they are 



