152 DB. F. P. MORENO AJfD MR. A. S. WOODWARD OX [Feb. 21 , 



Schropleura hrimetV, the bony plates and tubercles are still covered 

 only by epidermis, although most of them are reduced to small 

 nodules and might well have sunk more deeply into the abnormally 

 hairy skin. There is also reason to believe that in the gigantic 

 extinct Armadillos of the family Glyptodoutidse the same arrange- 

 ment of dermal structures prevailed ; for one specimen of 

 Panoclithiis tuhercuJatus obtained by Dr. Moreno for the La Plata 

 Museum actually shows the dried horny epidermis in direct 

 contact with the underlying boue, and seems to prove that the 

 numerous perforations in the Glyptodont dermal armour were 

 not for the implantation of hairs (as once supposed), but for the 

 passage of blood-vessels to the base of the epidermal layer. 

 Similarly, among the extinct Ground-Sloths of the family Mylo- 

 dontidse dermal ossicles have been found with the remains of 

 Ccelodon ^ and various forms (perhaps different subgenera) of 

 Mijlodon ; but the only examples of this armour 3^et definitely 

 described ' exhibit a conspicuously sculptured outer flattened face, 

 and it thus seems clear that Burmeister was correct in describing 

 them as originally reaching the upper surface of the dermis and 

 only covered externally by a thickened epidermis. Three such 

 dermal tubercles, now in the British Museum, are shown of the 

 natural size in PI. XV. tigs. 4-6. It is, however, to be noted that 

 Burmeister himself actually observed armour of this kind covering 

 only the lumbar region of the trunk. He believed that the other 

 parts of the animal were similarly armoured, because he had found 

 " the same ossicles " on the digits of the manus, where they were 

 "generally smaller and more spherical"; but he unfortunately 

 omits to make any explicit statement as to the presence or absence 

 of the characteristic external ornamentation on the latter. 



The omission just mentioned is especially unfortunate because 

 on careful comparison it is evident that the irregular dis- 

 position of the small ossicles in the piece of skin now under 

 consideration is most closely paralleled in the dermal armour of 

 the extinct Mylodon, as already observed by Drs. Moreno and 

 Ameghino. There is obviousl_y no approach in this specimen to 

 the definite and symmetrical arrangement of the armour such as 

 is exhibited both by the existing Armadillos and the extinct 

 Glyptodonts. There are, then, two possibilities. Either the 

 dermal armour of Mylodon varied in different parts of the body, 

 being sculptured and covered only by epidermis in the lumbar 

 region, while less developed, not sculptured but completely buried 

 in the dermis in the comparalivel)^ flexible neck and shoulder 

 region — in which case Dr. Moreno may be correct in referring 

 the problematical specimen to Mylodon ; or the dermal ossicles of 



^ A. Milne-Edwards, " Note sur une nouvelle Espece de Tatou a cuirasse 

 incomplete (Schropleura hruneti)," Nouv. Arch. Mus. vol. vii. (1871), pp. 177- 

 179, pi. xii. 



2 P. W. Lund, K. Dansk. Vidensk. Selsk. Afhandl. toI. viii. (1841), p. 85 

 (footnote). 



^ H. Burmeister, Anales Mus. Publico Buenos Aires, vol. i. (1864-69), p. 173, 

 pi. V. fig. 8. 



