A Remarkable Ground Sloth 



ii 



THORACIC MEASUREMENTS 



i 809-1 



Rancho la Brea to 



1825-1 

 Length of centrum 

 Depth of centrum 

 Greatest width of centrum 

 Across prezygapophyses 

 Total height 



Y.P.M. 13198 1 



Length of centrum ca. 33.0 



Depth of centrum 29.5 



Greatest width of centrum 44.5 

 Across prezygapophyses 



1 14.4 

 epiph. 



38.0 

 24.1 



128.6 



39-i 

 28.3 



1 137 



56.1 



1 19.0 



3 

 30.0 



38.1 



3i-3 

 107.9 



56.3 

 1 19.6 



5 

 3" 



387 

 34-5 



"3-5 

 59-7 



121.2 



7 

 32.5 



?434 41.5 43-7 



Total height 



41.0 



38.2 



123.4 



124.5 



9 



37-4 

 41.9 

 48.0 



53-5 



1 14.4 



est. 



11 



43-5 



41.6 

 120.0 



60.5 



J34-5 



11 



38.0 



50.0 

 59-0 



13 



43-9 



44.1 



132.6 



637 

 140.7 



13 

 39-0 



5i-2 



15 



44-3 

 46.3 



130.0 

 70.4 



151-8 



15 



39-4 

 47-5 

 55-o 



17 



47-3 

 48.8 



134-2 



78.7 

 160.6 



17 



43° 

 46.5 

 54-o 

 64.0 

 1 14.0 

 epiph. 



One peculiar feature is that in the Yale specimen the total height of the spines 

 does not seem to increase, whereas in the Rancho la Brea material, after the first, the 

 increase is steadily maintained from numbers 2 to 17. This again may be a juvenile 

 trait in the Yale specimen, correlated with less muscular development. The depth of 

 centrum in the Yale specimen is little less than that of Stock's, while the width is 

 less than half. 



The presence of dried tissue in the Yale specimen is highly interesting but inter- 

 feres with precise measurements, such as the depth of the centra. 



Lumbar Vertebrae. — The lumbars seem to agree with those of the Rancho la 

 Brea, except for size and proportions, wherein they vary, as do the thoracic vertebrae. 



Sacrum. — The sacrals are completely fused in each instance, and their spines 

 form a continuous crest. 



Caudal Vertebrae. — The caudals probably were twenty-one in number. The 

 most complete series from Rancho la Brea is sixteen in one specimen, Nos. 1-14, 16, 

 and 18. The Yale specimen now has Nos. 1-12. It is hoped, however, that explora- 

 tion will complete the series. 



In the Rancho la Brea specimens the transverse processes are long in the first two 

 caudals and much shorter in the third of the series and posteriorly. In the Yale speci- 

 men the diminution is evenly graded and not abrupt. 



r ibs — There are no points of divergence in either dorsal or sternal ribs. Out of 

 ten pairs of the latter we possess Nos. r, 3, 4, and possibly 10 of the right side and Nos. 

 1, 4, and half of another of the left. 



Sternum. — With the Yale specimen the manubrium and two other sternals are 

 present. The latter agree in being unsymmetrical pieces of bone. No N othrotherium 

 sternum is complete, but presumably the number of sternebrae was seven, which is 

 normal to other Pleistocene ground sloth genera. 



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