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Show 156 ON NEOMYLODON LISTAI FROM PATAGONIA. [Feb. 21, problematical skin mentioned by Dr. Moreno as having been taken to Upsala by Dr. Otto Nordenskjold \ It appears that with the skin was found the epidermal sheath of a large unknown claw, which may have belonged to the same animal. This specimen proves to be different from that of any existing Sloth, Anteater, or Armadillo, and is considered by Dr. Lonnberg to belong probably to the hind foot of a Mylodont, which did not walk on the exterior, lateral surfaces of the toes to the same extent as Mylodon. In a section of the skin provisionally ascribed to the leg, he observes that the small ossicles are very irregular, and shows two instances in which two are placed one above the other. In microscopical sections of the ossicles, however, he does not find the distinct Haversian systems of bone so conspicuous in m y slides; and hence he fails to remark the differences betAveen the structure of the armour in Neomylodon and Mylodon, which seem to me to be particularly noteworthy. His so-called " pigment cellules " in Mylodon are the dendritic infiltrations of oxide of manganese and stains of oxide of iron, to which I have made special reference. His observations as to the absence of a medulla in the hair confirm my own; but I have not seen any evidence of the suspected loss or disintegration of the hair-cuticle. Finally, Dr. Lonnberg has boiled a piece of the skin, thereby extracting glue, " which proves that the collagen and gelatinous substances are perfectly preserved." The latter observation confirms the evidence of the serum recorded above, and indicates that if the specimen is " of any considerable age, it must have been very well protected against moisture and bacteria."-A. S. W.] EXPLANATION OF THE PLATES. PLATE XIII. Neomylodon listai, Ameghino ; outer aspect of piece of skin, one half nat. size. PLATE XIV. D itto ; inner aspect of same specimen, one half nat. size. PLATE XV. Fig. 1. Neomylodon listai, Ameghino; transverse section of skin, nat. size, showing hair above and ossicles in lower layer. 2, 3. Ditto ; outer face of two ossicles, nat. size. 4-6. Mylodon, sp.; outer face of three ossicles, nat. size, one composed of two parts fused together. 4 a, 4 b. Inner and lateral aspect respectively of the specimen shown in fig. 4. 7. Neomylodon listai, Ameghino ; portion of horizontal section of ossicle, about X40. 7 a, 7 b. Haversian system and two marginal bone-lacunsB from the same, respectively X 85 and X 200. 8. Mylodon, sp.; portion of horizontal section of ossicle, about X 40. 8«. Three bone-lacunae from the same, X2U0. 1 E. Lonnberg, " O n some Remains of ' Neomylodon listai,' Ameghino, brought home by the Swedish Expedition to Tierra del Fuego, 1895-1897," Wissensch. Ergebn. schwedisch. Expect Magellansland. unter Leitung v. Otto Nordenskjold, vol. ii. pp. 149-170, pis. xii.-xiv. (1899). |