408 W. G. BTDEWOOD. 



to US in their completeness. They will bear a very close 

 comparison with the hairs of Tatusia (fig. 23)^ and are not 

 remarkably different from those of Tamandua (fig. 16) and 

 Dasypus sexcinctus (fig. 18). 



It is a curious fact that in all the American Edentates exa- 

 mined any characteristic features which each kind of hair 

 may possess is absent from the basal portion. The basal 

 parts of the hairs of Bradypus (figs. 5 and 6), Choloepus 

 (figs. 10 and 11), Myrmecophaga (fig. 15), and Toly- 

 peutes (fig. 22) agree Avith one another, and furnish a gene- 

 ralised type of hair structure, with which the whole hairs of 

 Tatusia, Tamandua, and Dasypus sexcinctus conform. 

 Since the hairs of Mylodon are in such close agreement with 

 this generalised type, it seems wiser to accept them as of 

 primitive and generalised structure than to attempt to estab- 

 lish a parallelism between them and those of the tree sloths, 

 especially in view of the fact that these latter are exti'emely 

 aberrant, and differ so remarkably inter se. There is no 

 need to conclude that Mylodon is the less a sloth, and more 

 related to the ant-eaters and armadillos, because its hairs fail 

 to possess an extra-cortex. 



As reo-ards the arrang-ement of the hairs in the skin there 

 is not much to be said. The hairs are, as has been pointed 

 out by Smith Woodwai'd (18, p. 149) and Lonnberg (7, p. 

 164), all of one kind, there being no under-fur, and they are 

 uniformly distributed, without any signs of symmetrical 

 grouping. In Bradypus the follicles of the small hairs are 

 clustered around those of the principal hairs, as Leydig (6, p. 

 707), Welcker (17, pp. 68—70, and pi. i, fig. 4), and de 

 Meijere (9, p. 361) have shown ; while in Choloepus the hairs 

 are arranged in bundles of two, though occasionally solitary, 

 and there is no proper under-fur. 



Appended to Dr. Sorby's remarks on Bradypus (15, 



p. 339) is afoot-note by the editor^ of the ^Linnean Society's 



Journal,' which reads, "There is a small sloth, however, in 



which the larger hairs are smooth and solid." It is much to 



• The late Mr. E. R. Alston. 



