334 A NEW MYLODON. 



Scapula. — Neither scapula is complete but the fragments put together 

 supplement each other. The general form and structure are sunilar to what 

 Owen has described and figured for M. robustus, but the dimensions differ slightly 

 as shown by the following : — 



Point of coracoid arch to anterovertebral angle 



Glenoid cavity to vertebral border, opposite spine 



Greatest length of glenoid cavity 



Greatest breadth of glenoid cavity 



Longest diameter of supraspinal aperture formed 



by union of acromion and coracoid 

 Shortest diameter of same 

 Greatest height of spine 

 Diameter of coracoscapular foramen 

 Long diameter of clavicular facet 



The spine divides the scapular surface nearly in halves, and is highest at the 

 point where the arch formed by acromion and coracoid, begins; that is, at about 

 30 mm. from the edge of the glenoid cavity. Its external edge is broadly flat- 

 tened, 25 to 21 mm. across, then slightly expands to 45 mm. opposite the 

 center of the aperture formed by the fusion of coracoid and acromion. In M. 

 robustus, this portion is somewhat wider. The remarkable fusion of the acro- 

 mion with the so called coracoid is characteristic of the sloths, and the homology 

 of the bones shows that the clavicle articulates as usual with the acromion proc- 

 ess, which has thus become greatly extended anteriorly and fuses with the 

 coracoid. The coracoscapular foramen is somewhat larger than in M. robustus. 

 This perforation is present in the anteaters as well as the sloths. Concerning 

 the homology of the so called coracoid in the mammals, Ameghino (1909), 

 Lydekker (1893), and Howes (1892) have made critical comparisons among 

 fossil and living Edentates and conclude that the bone to which this name has 

 been appUed is not the same as the coracoid of the Reptilia. Lydekker states 

 that in the sloth Bradypus, the coracoid forms part of the glenoid cavity, but 

 this should be verified. In a specimen of Myrmecophaga, in which the sutures 

 of the scapula are still discernible, the coracoid stands directly over the anterior 

 portion of the glenoid, but does not actually form part of it, since it is separated 

 therefrom by the epiphysis of the scapula, that extends forward underneath it. 

 The appearance is at first as if the coracoid formed the anterior portion of the 

 articulation, but this is seen on closer examhiation not to be the case. 



