_Ibid._ p. 347, 367. Footnote 4: _Ibid._ p. 337. Pl. 26. fig. 7. Footnote 5: Philosophical Transactions, vol. lviii. p. 34. (1768.) Footnote 6: Bridgewater Treatise, p. 139. Footnote 7: Geological Transactions, vol. iii. p. 437. pl. 44, 45, 46. Footnote 8: Quoted by Cuvier, Ossem. Foss. Ed. iv. tom. ii. p. 351. Footnote 9: Τοξον, arcus; οδους, dens. Footnote 10: Mem. de l’Acad. des Sciences de Paris, 1764, p. 568. Footnote 11: True fangs exist only in teeth of temporary growth, they may be one or more in number, but always diminish in size as they recede from the crown of the tooth, and are either solid, or with a very small canal. Footnote 12: This was written before an examination of the fragment of a lower jaw, forming part of Mr. Darwin’s collection of Fossil Remains, had led me to suspect that it was referrible to the genus Toxodon; should this suspicion prove correct, the four unequal incisors of the upper jaw are opposed to six equal sized ones in the lower. Footnote 13: I have ascertained that this elastic ligament exists in the neck of the Dugong. Footnote 14: The German Translator (See _Frorieps Notizen_., 1837, p. 119) of the abstract of my description of the Toxodon, published in the Proceedings of the Geological Society, asks, what is the _Mutica_ (misprinted _Muticata_), of Linnæus? The term is quoted from the Systema Naturæ, Ed. xii. p. 24. Linnæus first divides Mammalia into three groups, according to modifications of the locomotive organs, viz. _Unguiculata_, _Ungulata_, _Mutica_, and subdivides these, according to modifications of the dentary organs, into the orders, _Bruat_, _Glires_, _Primates_, &c. Footnote 15: Besides the relation to _food requiring much comminution_, which teeth with persistent pulps bear, they are also connected with the _longevity of the individual_. The term of life in a herbivorous animal, with grinders of temporary growth, is, of necessity, dependent on the duration of these essential aids to nutrition; thus, a sheep generally wears down its grinders in twelve years, and its natural term of life is consequently limited to about that period. Footnote 16: Μακρος _longus_, αυχην _cervix_: from the latter word Illiger derived _Auchenia_, his generic name of the Llama, Vicugna, &c. Footnote 17: