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UINTA SELENODONTS ° 



those of the preceding three, and has no distinct keel. The transverse pro- 

 cesses increase in size up to the penultimate vertebra, while the last one has 

 much shorter and straighter processes ; they are long, broad, depressed, and 

 curved strongly forward. The neural spines are rather low ; they incline for- 

 ward decidedly, except that of the last lumbar, which is nearly erect. The 

 zygapophyses are of the usual cylindrical, interlocking type, and I can dis- 

 cover no indication of the additional, or episphenial, processes which from the 

 faint beginnings in Poebrothermm have become so well developed in the exist- 

 ing camels. The sacrum is long and very much depressed and is composed 

 of three or four vertebrae. The anterior one has a broad, heavy centrum and 

 large pleurapophyses ; the posterior vertebrae are broad, flat, depressed, and 

 thin, with low, backwardly directed neural spines, and broad transverse 

 processes. 



The two anterior caudals, which are preserved in connection with the 

 sacrum, indicate a tail of moderate length ; they are short, but have complete 

 neural arches and spines, prominent zygapophyses, and very large transverse 

 processes, which have a backward curvature. Except for the greater size of 

 the transverse processes, these vertebrae are much like the corresponding ones 

 of Poebrotherium, and doubtless the tail was of similar proportionate develop- 

 ment in the two genera. 



IV. The Fore-Limb is short and slender, decidedly more so than the hind- 

 limb. The scapula is high and narrow, much narrower than in Poebrotherium ; 

 the neck is slender but not abruptly contracted ; the coracoid border, so far as 

 it is preserved, inclining much less strongly forward, in consequence of which 

 and of the position of the spine the prescapular fossa cannot be nearly so 

 wide as in the White River genus ; similarly, the glenoid border inclines but 

 little backward in its course above the neck. In Poebrotherium, on the con- 

 trary, both borders pursue a very oblique course, which gives great breadth 

 to the proximal portion of the blade. The spine is high and somewhat 

 recurved, making the anterior side convex and the posterior concave ; the 

 acromion is both long and high, projecting somewhat outward as well as 

 downward, but does not descend nearly to the level of the glenoid cavity, 

 and terminates in a blunt and very slightly recurved point. The acromion is 

 thus very much smaller than in Poebrothermm, in which the process is far 

 longer, descending to the level of the glenoid cavity, and is much broadened 

 and thickened at the end. The glenoid cavity is quite deeply concave, and, 

 as in the White River type, of nearly circular outline. The coracoid is quite 



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