STRUCTURE OF THE HAIRS OF MYLODOX LISTAI. 393 



On the Structure of the Hairs of Mylodon 

 Listai and other South American Edentata. 



By 



W. G. Ridewood, D.Sf., F.L.S., 

 Lecturer on Biology at the Medical School of St. Marj's Hospital, London. 



With Plate 2G. 



The interest attaching to tlie discovery of portions of well- 

 preserved skin of a great Ground Sloth, very closely allied to 

 if not identical with Mylodon, was considerably increased 

 when it was found that the hairs do not agree in their minute 

 structure with those of the Tree Sloths, Brady pus and 

 Choice pus. While agreeing with the latter in the absence 

 of a definite medulla, they are destitute of the extra-cortical 

 layer which characterises the hairs of Bradypns, and have 

 not the fluted surface which is such a distinctive feature of 

 the hairs of Choloepus. The characters of the hairs have 

 been commented upon by several authors in the course of 

 their remarks upon the remains of this ground sloth, but the 

 subject has never been treated exhaustively ; and Professor 

 Ray Lankester suggested to me that the matter was worthy 

 of further inquiry, and that it was desirable to compare the 

 newly discovered hairs not only with those of Brady pus 

 and Choloepus, but also with those of the ant-eaters and 

 armadillos. 



The order PJdentata, as at present constituted, will proba- 

 bly prove to be an unnatural assemblage of animals, and it 

 may become necessary, when our knowledge is more complete, 



VOL. 44, PART 3. — NEW SERIES. C Q 



