THE MAMMALIA OF THE UIXTA FOIJMATIOX. 515 



7th and lOtli (Fig. 2), The centrum is opisthocd'lous and considerably excavated at 

 the sides ; the antero-posterior and transverse diameters are al)out the same ; the 

 lower half of tlie spine is preserved, it is a stout triangle in section indicating a great 

 length and strongly oblique inclination; the zygapophyses are almost horizontal. One 

 of the 1 u m tj a r centra preserved is considerably longer than the abovc-descrilied 

 dorsal, and has a stout keel ; the spine is broad (Fig. 4) and grooved posteriorly ; 

 the zygapophyses are rounded and vertically placed. 



These vertel^ral characters closely repeat those observed in Palceosyops, except 

 that the cervical centra, while nearly double in height and breadth, are only a tritle 

 longer. In Titanotherinm the cervicals are not further shortened, but retain {\\v pro- 

 portions seen in JJiplacodon ; they are, if anything, somewhat longer. The dorsal 

 spines are still more elongate, forming a great hump which was incipient in Pithvo- 

 syop.^ and probably well developed in Diplacodon. 



Two ribs are pi'cserved which belong respectively in the anterior and middle 

 region of the chest. They are much lighter and more rounded than in Titanothcriinn. 

 The complete rib from the midregion has a subquadrate section in the up])er thiixl of 

 the shaft, and an oval section in the lower third ; it does not show the extreme flat- 

 tened oval seen in Titanotherium ; the length, not allowing for curvature, is 71 era., 

 showing that the deplh ol' the chest was about thii'ty inches. 



Platk IX. 



Scapula (Fig. 12). Both scapuliB are preserved, but the superior and lateral 

 borders are incomplete. The coracoid process is a stout tuberosity. The glenoid 

 fos.sa is an elongate and rather shallow oval. The spine ascends very gradually from 

 the neck and passes without an acromial process into a deep recurved ridge ; in a 

 midsection the spine is much expanded along the border and ovcihaugs the post- 

 8cai)ular fossa. The })ai-ts preserved indicate that the scajmhi was lofty, with a 

 rounded supraseajnihir lioidci- unlike the sonu wlial angular lioidi r of l^itaiiot/icrium 

 and without any di.stinct indentations such as are seen in lihinoctros. 



Ifumerus (Figs. 11 and 11a). The humerus lacks the head, lesser tuberosity 

 and bicipitaj groove. There is a stout deltoid ridge terminating in a prominent re- 

 curved hook. The shaft is iwisted upon itself as in Ilhinoceros, that is the major 

 diameter passes obliipiely from the outer posterior lo the inner anterior siile. The 

 supinator ridge is less distinctly marked than in lihiuoceros and less prominent than 

 in Titanot/ierium. The pronator ridge is also rugo.se but not ])rojecting. The supra- 

 trochlear fo.ssa is deeply excavated and the tiochlear surfaces are somewhat oblique 

 to the main axis of the .shaft. 



