THE MAMMALIA OF THK DEEP RIVEK BEDS. 135 



section ; posteriorly, they become longer, much more slender and of more rounded 

 section. Nothing is known of the sternum. 



The Fore Limb displays some characters of unexpected interest. The scapula 

 varies considerably in the different specimens, some of which variations would appear 

 to be of a sexual nature. 



The best preserved shoulder-blade (PL IV, Fig. 33) is one which belonged, as 

 I believe, to a female, being associated with a skull in which the small size of the 

 canines and the caniniform first lower premolar is very striking. In this specimen 

 the coracoid and suprascapular borders are broken in such a way as to prevent an 

 accurate determination of the outline of the bone, but the spine, neck, and most of 

 the postscapular fossa are in good condition. The glenoid cavity is small, shallow, 

 and of nearly circular shape, the antero-posterior diameter but slightly exceeding 

 the transverse. The coracoid is large, especially in the vertical dimension, but is 

 not clearly demarcated from the neck of the scapula and displays but little rugosity ; 

 hence it is not conspicuous when viewed from the outer side. The neck of the 

 scapula is high in the vertical direction, narrow and contracted, and the rugose lines 

 for muscular attachment are but faintly marked. Above the neck, the glenoid bor- 

 der extends obliquely upward and backward, enclosing with the spine a narrow, 

 triangular postscapular fossa. This border is considerably thickened and its external 

 margin is elevated, making the fossa quite concave antero-posteriorly. The spine 

 is very high, and for most of its length curved backward, so as to make the anterior 

 surface convex and the posterior concave. Its free margin is flattened and gradually 

 becomes wider inferiorly to the point where it sends out a distinct metacromial pro- 

 cess. ]STo other genus of the family has yet been found in which a metacromion 

 occurs. Beneath this process the curvature of the spine is reversed, the posterior 

 surface now being convex and the anterior concave, and the acromion projects for- 

 ward as well as downward. The length of the acromion cannot be definitely stated, 

 as its tip is broken away, but obviously it could not have descended nearly to the 

 level of the glenoid cavity. 



This spine is of a very exceptional character for an artiodactyl. In Oreodou 

 there is no metacromion, the spine is lower and not recurved and descends more 

 nearly to the level of the glenoid cavity. In Fporeodon there is likewise no meta- 

 cromion, but the spine is very high and curved in very much the same fashion as in 

 Mesoreodon. 



The second specimen (PL IV, Fig. 34) has lost the spine but preserved the entire 

 outline of the scapula, which is represented either by bone or by the impression of it 

 in the matrix. There is good reason to believe that this specimen should be referred 



A. P. S. — VOL. XVIII. R. 



