Speaking of this tooth, Cuvier observes, “Je l’avois cru d’abord nécessairement _de paresseux_; mais aujourdhui que je connois mieux l’ostéologie des divers _tatous_, je trouve qu’elle ressemble au moins autant à une dent de l’un des grands _tatous_.”—Loc. cit. p. 172. Footnote 34: Synopsis Mammalium. Footnote 35: It is most probable that the substance which is here termed “enamel,” is similar to that which forms the dense prominent ridges in the tooth of the Megatherium, and which I have shown to be composed of minute parallel calcigerous tubes, similar to the ivory or bone of the human tooth. Footnote 36: Medical and Physical Researches, pp. 323–4. Footnote 37: Loc cit. p. 330. Footnote 38: Spix and Martius, Reise in Brazil, Band ii. p. 5. Footnote 39: Harlan’s Medical and Physical Researches, 1835, p. 334. M. de Blainville speaks of a cast of a fragment of a lower jaw “portant encore _cinq_ dents en série;” as having been transmitted to the Museum of the Garden of Plants from North America, together with other bones, all of which he refers to the genus _Megalonyx_; M. de Blainville does not describe these teeth, which is to be regretted, inasmuch as, if he be correct in regard to their number, which can hardly be doubted, and if he wrote with any clear and definite ideas of the generic characters of _Megalonyx_, this would indicate that _Megalonyx_ differed generically both from _Megatherium_ and _Mylodon_ in a more important dental character than has hitherto been suspected (See “Comptes Rendus, &c.” 1839, No. V. p. 142.) Footnote 40: Dr. Harlan also indicates differences in certain parts of the skeleton of the New York fossils as compared with his _Meg^x. laqueatus_; but thinks them probably due to a difference in the age of the individuals: he says “There is also in Mr. Graves’ collection, in New York, a tibia, nearly perfect from the right leg; the segment of a flattened sphere, on which the external condyle of the femur moves, is rather more depressed, than in the specimen from Big-bone-cave. Other marks and peculiarities are observable on this bone, not found on that of the _Megalonyx laqueatus_ of Big-bone-cave, but they are probably due to a difference in the age of the individuals.” Loc. cit. p. 335. Footnote 41: Μυλη, _mola_; οδους, _dens_. Footnote 42: If the lower jaw of _Mylodon Harlani_, bears the same proportion to its teeth as does that of _Mylodon Darwinii_, it must be about two feet in length. Footnote 43: See Proceedings of the Geological Society, March 1839, and Parish’s Buenos Ayres, p. 178, _b_, Pl. 1, fig. 2 and 3. Footnote 44: Σκελις, _femur_; Θηριον, _bellua_; in allusion to the disproportionate size of the thigh-bone. Footnote 45: