158 LÖNNBERG. SOME REMAINS OF NEOMYLODON LISTAI. 



If we now conipare the sections described above with 

 those of the true fossil Mylodon we see at once that the like- 

 ness of the microscopical structure is also very striking. As 

 a result of their great age the Mylodon ossicles are brownish 

 and not so translucent. Neither are the structures so sharply 

 defined in these old ossicles because the organic matter has 

 more completely been spoiled (fig. 9). But we can easily re- 

 lind and identify every part of the structure observed in 

 »Neomylodon». 



The peripherical lamelke (»äussere Grundlamellen» of 

 German authors) seem to be better developed in Mylodon, 

 but this is perhaps only caused by higher individual age. 

 The main mass is traversed by the same bundles of fibrils 

 of connective tissue, the canals for the vessels are alike etc. 

 The correspondance is thus complete in nearly every detail. 

 Here is however one thing which is characteristic for these 

 Mylodon ossicles and which is not found in the »Neomylodon», 

 namely, pigment cellules. These cellules are much larger 

 than the bone-corpuscles and have the typical appearance 

 with richly branched processes (fig. 9). The colour of the 

 pigment is very dark brown so that the cellules look almost 

 black. The Situation of these cellules in a piece of bony 

 tissue is rather remarkable, but it can probably be explained 

 in the following way. The pigment cellules have, from the 

 beginning, belonged to the connective tissue of the cutis, but 

 when the ossification took place they became imbedded in 

 the ossicles like the (Sharpey's) fibrils and other elements 

 which from the beginning belonged to the connective tissue. 



All taken together we find that it is only the difference 

 in shape, the small round, superficial depressions, and the 

 presence of these pigment cellules which distinguish the os- 

 sicles of Mylodon from those of »Neomylodon» and this dis- 

 tinction can hardly be of more than specific value. 



A comparison between sections through the »Neomylodom- 

 ossicles and sections through the scutes of JDasypus sexcinctns 

 reveals, on the contrary, a very great difference. This con- 

 sists mainly in the scutes of the Dasypus being composed of 

 bony tissue of quite typical structure. As well the main 

 lamellte (»Grundlamellen») as the lamellous Systems round 

 the Haver's canals are well developed, as has already been 

 observed by several authors. These scutes are not so com- 



