A NEW MYLODON. 335 



The clavicles are broken, but the portions articulating with the acromion 

 are present. This articulation was by a convex facet slightly constricted off 

 from the shaft of the bone, and elliptical in outline. The shaft is elliptical in 

 section becommg slightly flattened, and apparently more slender than in M. 

 robustus. 



The humerus is essentially similar to that of M. robustus, but is perhaps a 

 little smaller as nearly as can be determined in its shattered condition. In side 

 view the head is nearly hemispherical, but from the dorsal aspect is seen to 

 have the condylar surface mainly on its inner half and tapers anteriorly to con- 

 form to the general outline of the glenoid cavity of the scapula. Its longest 

 diameter is HI mm. The great development of the deltoid crest in M. robustus 

 is seen likewise in this species. The pectoral crest seems to be less pronounced. 

 From the trochin to the distal end of the deltoid rugosity is 275 mm., against 

 about 256 in Owen's species. From the latter point to the tip of the rounded 

 portion of the condyle is about 155 nun., giving a total length of about 430 mm. 

 for the entire humerus. Owen gives about 445 for M. robustiis. The distal 

 end has the same pecuUar articulating surface, the outer half rounded, more than 

 half a circumference in its anteroposterior extent, the inner half nearly flat. 

 The entire articular surface is 125 mm. in transverse extent, which is about as in 

 M. robustus. 



The ulna is represented by the proximal portion only. The most striking 

 difference in comparison with M. robustus is the greater length of the supe- 

 rior, flattened articular surface which is much longer than broad (diameters 

 97 X 55 nmi.), instead of about as broad as long; while the inferior concave 

 articulation is likewise proportionately narrower and is actually separated from 

 the superior facet. A deep depression lies between the two. This inferior articu- 

 lating surface is contiguous anteriorly with a smaller one, nearly round and 

 flattened in the frontal plane, that serves for articulation with an elliptical facet 

 at the proximal border of the radius. The ulnar has therefore three distinct 

 articulating facets at the proximal end, two for contact with the humerus and 

 one for contact with the radius. To judge from Owen's figure of Mylodon ro- 

 bustus the radial facet seems to be distinct from that for the humerus instead of 

 confluent with it. 



The radius is sunilar to that of M. robustus in size and shape. The proxi- 

 mal end is an elliptical concave facet, whose diameters are 71 and 50 mm. re- 

 spectively, for articulation with the hmnerus. On the ventral border of this 

 is the small elUptical articulation for the ulna. Distally the radius gradually 



