EDENTATA OF THE SANTA CRUZ BEDS. 315 



A single segment of the mesosternum is preserved ; the body, or dorsal 

 part, of the segment is relatively short, broad and thin, but the ventral 

 projection which carries the facets for the tubercles of the sternal ribs is 



exceedingly prominent. 



MEASUREMENTS. 



? Fourth thoracic, length of centrum. . . .015 Last thoracic, length of centrum 017 



width of anterior face . .014 width of anterior face.. .023 



" " posterior face .017 " " posterior face. .026 



" over transverse " over transverse 



processes 035 processes 040 



height of neural spine " height of spine from 



from centrum 02 1 centrum 029 



width of neural spine " width of spine at base. . .019 



at base 015 " " " ' tip ... .0115 



width of neural spine 



at tip oio 



The scapula has lost the distal epiphysis with the coracoid, and the 

 glenoid border is much broken, but the shape of the bone is evidently 

 different from that of Hapalops in its shortness and breadth ; the spine, 

 which for the proximal third of its course is hardly noticeable, is so placed 

 as to make the prescapular fossa much larger than the postscapular, and 

 the glenoid border is, as usual, elevated into a prominent ridge. 



The humerus (Plate LIII, fig. 3) also differs notably from that of Hap- 

 alops; the head is relatively large and projects well behind the plane of 

 the shaft, and the internal tuberosity is unusually large ; the deltoid area 

 is less developed than in any other of the known Santa Cruz Gravigrada, 

 and, though of the usual length, its borders are not at all prominent. 

 The shaft is quite stout, diminishing in size distally, until it is greatly 

 broadened by the supinator ridge ; this ridge, the internal epicondyle and 

 the foramen are much as in the other genera, but the external epicondyle 

 is unusually prominent. The trochlea is quite peculiar and more nearly 

 approximates that of Megalonyx than does the trochlea of Hapalops; 

 compared with the latter, it is narrower and more than half of its breadth 

 is taken up by the prominent, hemispherical facet for the radius ; the ulnar 

 facet is narrower, much more convex transversely, and its inner border is 

 not produced into a flange ; the anconeal fossa is very small and shallow. 



As the ulna (Plate LIII, fig. 4) has lost both epiphyses, its length is 

 not determinable ; the olecranon was, however, obviously shorter than that 



