STRUCTURE OF THE HAFRS OF MYLODON LISTAI. 395 



act as the type of the genus. Glossotherium, a genus 

 founded by Owen in 1840 (11, p. 57), is admitted by himself 

 (12, p. 154) to be identical with Mylodou Darwiuii, and 

 this genus may thus be dismissed as a synonym of Mylodon, 

 The same fate befalls Neomylodon, since the newly dis- 

 covered specimens to which the name was applied are widely 

 regarded as generically,if not specifically (Nordenskjold [10] ), 

 identical with Owen's Mylodon Darwinii. Until, however, 

 the specific identity has been more fully established it is 

 preferable to retain Ameghino's specific name of Listai for 

 these remains. 



The hairs of Mylodon Listai have been described by 

 Lonnberg (7), Jacob (4), and Smith Woodward (18 and 19), 

 and transverse sections have been figured by the first two 

 authors. The descriptions presuppose a knowledge of the 

 hair structure in Brady pus, the ant-eaters and armadillos, 

 and so in the present communication the consideration of 

 the Mylodon hairs and the criticism of the views of these 

 three authors are left till the last. 



The method adopted for the examination of the hairs was 

 in all cases the same. The hairs were arranged with the 

 roots pointing one way and the free ends the other ; they 

 were tied up in bundles, stained with a weak alcoholic 

 solution of magenta, washed and dehydrated. The bundles 

 were then soaked in x3'lol, and transferred to hard paraffin. 

 After cooling the paraffin was cut into convenient blocks, 

 and the sections were made by hand with a sliding motion of 

 the razor. It was found that better results were obtained in 

 this way than by the employment of any form of microtome. 

 Some of the sections were mounted in glycerine jelly, but the 

 majority in Canada balsam, since the former medium has the 

 disadvantage of dissolving out the stain. A few hairs of 

 each of the species studied were stained and mounted whole. 

 For the Mylodon hairs I am indebted to the kindness of Dr. 

 F. P. Moreno ; the hairs of the other Edentata were obtained 

 from dried specimens in the Natural History Museum, 

 London. 



