EVOLUTION OF THE SKELETON OF EOCENE AND OLIGOCENE TITANOTHERES 



633 



rise to Mesatirhinus and Dolichorhinus, and although 

 broader than in Mesatirhinus is separated from that 

 of Palaeosyops by many trenchant characters, the 

 resemblances to that form being chiefly homoplastic or 

 analogous. The width of the carpus (79 mm., esti- 

 mated) is intermediate between that of MesatirMnus 

 (65 to 72) and of Palaeosyops (95), but nearer the 

 former than the latter. The superior facets of the 

 carpals and metacarpals are flatter than in Palaeosyops 

 and relatively wider posteriorly. More in detail, the 

 scaphoid (Am. Mus. 12204) in superior view is more 

 shallow anteroposteriorly, being suboval, with broad 



A2 ^- — ^-^ Ba 



Figure 652. — Seventh cervical vertebra of Manieoceras man- 

 teoceras compared with that of Palaeosyops leidyi 



Ai, A2, M. manieoceras, Am. Mus. 12204; anterior and posterior views. Bi, B2 

 P. leidyi, Am. Mus. 1562; anterior and posterior views. One-third natural size. 



ends, whereas in Palaeosyops it is elongate anteropos- 

 teriorly, with pointed ends; the facet for the magnum 

 is relatively broader, that for the trapezoid more hori- 

 zontal than in Palaeosyops. The lunar (No. 12204) 

 has the facet for the magnum more vertical and that 

 for the unciform more horizontal than in Palaeosyops; 

 its posterior face is relatively deeper and much nar- 

 rower, but not so much so as in MesatirMnus. The 

 cuneiform (Am. Mus. 12216) differs from that of 

 Palaeosyops in the following particulars: The superior 

 (radial) facet is not produced antero-internally into a 

 ridged prominence, is deeper anteroposteriorly near the 



external end, and is separated from the broad pisiform 

 facet by a high keel; of the two facets for the lunar 

 the upper one is comparatively deep vertically, the 

 lower one is very shallow; the unciform facet is deeper 

 anteroposteriorly. As compared with that of Mesati- 





FiGUEE 553. — Left humerus of Manieoceras 7nan- 



ieoceras 

 A, Am. Mus. 12384; Bridger C 3; front view. B, Am. Mus. 12204; 

 Bridger D 2; front (Bi), and outer side (Ba) views. One-si-xth 

 natural size. 



rJiinus the cuneiform is much broader, but a subfamily 

 agreement is seen in the detailed characters of the 

 facets. The pisiform is not preserved. In the trape- 

 zoid (Am. Mus. 1587, 12216) the trapezium facet is 

 confined to the postero-external part of the bone and 



554. — Right manus of Man- 

 ieoceras manieoceras 

 Chiefly from Am. Mus. 1587; Bridger C or D. Scaph- 

 oid, lunar, and magnum chiefly from Am. Mus. 

 12204. The magnum itself and the scapho-magnum 

 contact as represented are somewhat too broad to 

 fit well in 1587. Ai, Front view of manus; A?, 

 phalanges of median digit; As, outer side view of 

 metacarpal V; Ai, second phalanx of digit V. One- 

 third natural size. 



is broadly and roundly continuous above with ihe 

 scaphoid facet, whereas in Palaeosyops it extends 

 nearer to the front face of the bone and meets the 

 scaphoid facet supero-anteriorly at an acute angle. 

 In Manieoceras also the front face of the trapezoid 

 is not carried obliquely downward and inward 



