APPENDIX A 309 



may be observed to radiate regularly outwards. Numerous small vascular 

 canals, frequently branching, are cut in various directions ; and the 

 bony tissue, which is developed in every part of the ossicle, exhibits 

 abundant lacun^u. Nearly everywhere, except in the narrow peri- 

 pheral area just mentioned, it is easy to recognise the bony laminae 

 arranged in Haversian systems round the canals ; and most of the lacuna? 

 between these lamina? are excessively elongated, with very numerous 

 branching canaliculi, which extend at right angles to their longer axis. 

 Near the margin of the ossicle, especially in its more translucent parts, the 

 bone-lacunae are less elongated, more irregular in shape, and apparently 

 not arranged in any definite order. There is no clear evidence of 

 bony laminae concentric with the outer margin, though appearances 

 are sometimes suggestive of this arrangement. A vertical section of an 

 ossicle presents exactly the same features as the horizontal section now 

 described. It is thus evident that the vascular canals with their Haversian 

 systems of bone have no definite direction, but are disposed in an 

 entirely irregular manner. 



Taking into consideration all characters, and making comparisons 

 with the aid of my friend Mr. W. E. de Winton, I am inclined to regard 

 the fragmentary specimen as the skin of the neck and shoulder-region 

 with part of the left clieek. The apparent bilateral symmetry between at 

 least part of the thickened anterior outer angles of the specimen has 

 already been noted ; and if this observation be well founded, the middle line 

 of the back extends vertically down the middle of the photograph, p. 306. 

 If the rounded notch above B be the base of the external ear, as seems 

 probable, the thick wrinkled skin (C) with fine short hair still further to 

 the left must be the cheek. The ear and cheek on the right side have 

 been removed ; but at the base of the outwardly-turned angle on this side 

 of the specimen there are the very long hairs which occupy a similar 

 position on the left. It thus seems possible to estimate the transverse 

 measurement between the cars as from 0.25 m. to 0.30 m., which corre- 

 sponds with a tentative estimate of the same distance in Mylodon robiistiis 

 based on a skull in the British Museum. 



(b) Coiuparisoiis and Gcticral Conclusions. 



The skin now described differs from that of all known terrestrial 

 Mammalia, except certain Edentata, in the presence of a bon\' dermal 

 armour. There can therefore be little doubt that the specimen has been 

 rightly referred to a member of this typically South .\merican order. 

 Even among the ICdentates, however, the hagment uow under considera- 

 tion is unique in one respect ; for all the ossicles are buried deeply in the 



