73 



the ischium ; this is not therefore an instance of the exclusive resemblance of the 

 Sloths to the Mylodon. In the great length and continuous spinous crest of the 

 sacrum, the Mylodon strikingly resembles the Armadillos, but here any special 

 affinity, as indicated by the pelvis, ceases ; the iliac bones in the loricate Eden- 

 tata are straight, strong, narrow prismatic beams, well adapted for transmit- 

 ting the weight of the sacrum and carapace to the acetabulum and thigh-bone. 

 In the Mylodon these bones are, as we have seen, relatively more expanded 

 than in the Sloths, which have the broadest iliac bones amongst existing Eden- 

 tata ; in this part of their osteology the Megatherioids resemble the Proboscidian 

 Pachyderms. 



By the anatomists who have favoured the view of the affinities of the Mega- 

 therium to the Armadillo-tribe, the small Chlamyphorus truncatus has been selected 

 as its especial representative in the existing creation. I have therefore submitted 

 the skeleton of this extremely rare species to a close examination and comparison 

 with that of the Mylodon. 



It is true that the Chlamyphore resembles the Mylodon more than the Arma- 

 dillos do, in the greater expansion of the iliac bones ; but the direction or aspect 

 of the expanded part is quite different from that in the Mylodon, and the Chla- 

 myphorus deviates, more than other Armadillos, from the type of the Mylodon 

 and Sloths in the disunited pubic bones, and in the singular development and 

 supplemental junction of the posterior part of the sacrum to the ischia, viz. by 

 the spinous as well as the transverse processes. The ilium in the Chlamyphorus 

 extends in the form of a straight vertically compressed plate from the anterior 

 part of the sacrum to the acetabulum, hereby essentially according with the 

 Armadillo-type ; the broad and thin lamelliform process rises from the ilio-sacral 

 anchylosis and from the upper or posterior border of the ischiadic foramen, and, 

 after ascending vertically a short distance, terminates by bending outwards : 

 these ilio-ischial plates have an obvious relation to the support of the unusually 

 expanded posterior part of the bony carapace, and have consequently no analogues 

 in the Megatherium or Mylodon. The spines of the sacral vertebrae form a conti- 

 nuous ridge, as in the Mylodon, but the proportions are reversed, the ridge being 

 higher at the posterior than at the anterior part of the sacrum ; along the ante- 

 rior half of the sacrum also, in the Chlamyphorus, two parallel ridges are deve- 

 loped, corresponding in position to the oblique processes of the preceding ver- 



