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University of California Publications in Geology [Vol. 10 



of parts, for extending vertically downward from the haemal trough 

 and piercing the bone is a short canal which opens distally between 

 the arms of the broad base. Only one of the arms, forming the 

 sides of the haemal trough, is preserved in the Hawver Cave specimen 

 and it bears an anterior and a posterior facet for the caudal vertebra. 



It would appear from the chevron-bone preserved that the tail 

 of Nothrotherium received better support than did that of a type 

 like Mylodon. 



Measurements op Chevron Bones 



No. 21474 No. 21475 



Greatest depth 59.8 mm. 67.8 



Greatest anteroposterior diameter of proximal end 45.5 43.7 



Transverse diameter at middle 20. 19.6 



Greatest transverse diameter of distal end 54.7 



The sternum is represented by several separate elements, one of 

 which (figs. 23a., 235, 23c) is well preserved. This specimen, no. 

 19890, resembles mesosternal segments of Hapalops very closely in 

 shape. No. 19890 is decidedly smaller than mesosternal segments of 

 Mylodon. The flattened dorsal portion of the specimen from Hawver 

 Cave is practically square with concave lateral margins and thickened 

 anterior and posterior ends. At one end there is some indication of 

 articulating surfaces on the ventral side and toward each of the lateral 

 margins. With these exceptions there are no large and distinctly 

 defined facets present at the corners of the ventral surface for sternal 

 ribs as in the mesosternal segments of Hapalops and Mylodon. The 

 ventral head of the pawn-like segment possesses four facets articulat- 

 ing also with sternal ribs. 



Measurements of Sternal Segment, no. 19890 



Greatest length of base 43 mm. 



Greatest width of base 48 



Depth 40 



Greatest anteroposterior diameter of ventral head 30.7 



Greatest transverse diameter of ventral head 41.6 



Although the humerus, no. 10631, is but a trifle shorter than the 

 corresponding element of Megalonyx, no. 21003, from Kancho La 

 Brea, and shorter than specimens of M. jeffersoni described by Leidy, 

 the shaft is comparatively very slender and the distal third much 

 less expanded. Nothrotherium differs decidedly more from Hapalops 

 in slenderness of shaft of the humerus than does Megalonyx. In 

 anterior view, figure 24a, the head of the cave specimen is not as 



