STRUCTURE OF THE HAIRS OF MYLODON LISTAI. 405 



in D. sexcinctus;^ the cuticle, also, is considerably thicker. 

 In both species the granules in the cortex are most thickly 

 set at some little distance from the margin, thus leaving a 

 central part and a peripheral part of the cortex relatively 

 clear. The long diameter of the oval measures about 230 ju 

 in both species. 



Tolypeutes conurus. 



Tolypeutes has solid hairs provided with a thin, finely 

 scaled cuticle. The minute structure very closely resembles 

 that of the Dasypus hairs ; in facr, except for their lighter 

 colour, these hairs might be considered as of intermediate 

 character between those of the two species of Dasypus 

 examined. The sections are oval in shape (fig. 20), and 

 there is a central clear area suggesting a medulla such as 

 occurs in Dasypus villosus, but it has no cavity, and does 

 not stain differently from the cortex. The cortex contains 

 bright granules, not of a brown colour, disposed most thickly 

 around the centi-al clear space. Nearer the base of the hair 

 the section is circular (fig. 22), and has no central clear area. 

 The width of an average hair at its broadest part is 200 ju. 



Tatusia novenicincta and pilosa. 



The hairs of Tatusia are cleai-, solid, and non-medullate, 

 with a sharply marked cuticuhir scaliug and a very faint 

 longitudinal striation. In transverse section the cortex 

 appears very clear, and contains only a few highly refractive 

 colourless granules (fig. 23). These are uniformly distributed, 

 and are particularly scarce in Tatusia novenicincta. The 

 sections of the hairs of T. pilosa are oval, and measure lloju 

 X 95 /u ; while those of T. novenicincta are circular ita shape, 

 and measure 130/i across. 



Mylodon Listai. 



The hairs of Mylodon Listai are solid, and without any 



' Lonnberg (7, p. 162) speaks of D. sex cine tus as though its hair§ 

 possessed a central pith. 



