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Show 1899.] NEOMYLODON LISTAI FROM PATAGONIA. 151 lacunas. Nearly everywhere, except in the narrow peripheral area just mentioned, it is easy to recognize the bony lamina? arranged in Haversian systems round the canals ; and most of the lacuna) between these laminae are excessively elongated, Avith very numerous branching canaliculi, which extend at right angles to their longer axis. Near the margin of the ossicle, especially in its more translucent p;trts, the bone-lacunas are less elongated, more irregular in shape, and apparently not arranged iu any definite order (PI. X V. fig. 7 b). There is no clear evidence of bony lamina) concentric with the outer margin, though appearances are sometimes sugges-tiAre of this arrangement. A vertical section of an ossicle presents exactly the same features as the horizontal section nowT 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 m y 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 cheek. 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 verti-cally down the middle of the figure, PI. XIII. If the rouuded 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 ears as from 0*25 m. to 0-30 m., which corresponds with a tentative estimate of the same distance in Mylodon robustus based on a skull in the British Museum. (b) Comparisons and General Conclusions. The skin now described differs from that of all known terrestrial Mammalia, except certain Edentata, in the presence of a bony dermal armour. • There can therefore be little doubt that the specimen has been rightly referred to a member of this typically South-American order. Even among the Edentates, however, the fragment now under consideration is unique in one respect; for all the ossicles are buried deeply in the lower half of the thickened dermis and the hairs are implanted in every part of its upper half, whereas all the forms of bony armour hitherto described in this order reach the outer surface of the dermis and are merely invested with horny epidermis. This is the case, as is well known, in the common existing Armadillos, in which the hair is only implanted in the dermis between the separate parts of the armour. Even in the unique and remarkable skin of an Armadillo from Northern Brazil, described by Milne-Edwards under the 'name of |
