354 R. S. Lull — Pleistocene Ground Sloth, 



Eighth ? caudal. — The smallest caudal preserved is the 

 eighth or ninth. Here the centrum is somewhat hexagonal, 

 deeply excavated below, with a narrow bridge of bone con- 

 necting the anterior and posterior (chevron) hsemapophysial 



facets. This closure is variable. 



FlG * 8 * Owen speaks of it in Mylodon 



^ P^ robustus as being present in the third 



\%4^F(7 to tne niuth inclusive, or, as he 



J- — ^p^\l expresses it, in these vertebrae the 



/ • \^ spinal artery pierces the angle on 



c — .~fh j M;;.;:;:'--' either side of the ventral depres- 



""^^z-^Xf})/^ sion. In the material before me a 



a i.^> canal is formed in the second, 



eighth and ninth, and not in the 



Fig. 8. Eighth ? caudal fourth, fifth, sixth and seventh. 



vertebra of Mylodon harlani. Thig ma Dowever , be an individual 



One-fourth nat. size. Letter- . , • * 7 ,-, ' j , ■, ti 



in as in fi „ 7 variation, as the caudals probably 



did not pertain to one animal. 



The neural canal is somewhat smaller relatively to the bulk 

 of the centrum and is nearly circular in section, although the 

 posterior face thereof rises in such a way as to occlude the 

 lower half of the canal when the vertebra is viewed directly 

 from the rear. The anterior zygapophyses are large and heavy 

 and their slightly curved facets look more directly inward than 

 before owing to the reduction of the horizontally expanded 

 lower portion. The postzygapophyses have been lost and the 

 vertebra is abraded in such a way that there is little indication 

 of their presence. The same is true of the spinous process, 

 which could not, however, have been prominent. 



The transverse processes are broken off, but their base shows 

 them to have been well developed and to have extended along 

 the entire length of the centrum, excluding the epiphyses. 

 The hsemapophysial facets are well developed, betraying the 

 presence of chevron bones of considerable size. The anterior 

 pair of facets is the longer in antero-posterior extent. 



Dimensions. 



Centrum, length 50 mra 



depth ._ 55 



breadth _ 63 



Neural canal, height ._ 12 



width _ 14 



Neural arch, width over pedicels 35*5 



u " prezygapophy ses 49 "5 



Total height of vertebra as preserved 84 



