| Plate [I.] | Cranium of Toxodon Platensis, nat. size, basal view, with the sixth molar, right side upper jaw, and grinding surface of the seventh molar left side. |
| [II.] | Cranium of Toxodon Platensis, side view. |
| [III.] | Ditto, upper view. |
| [IV.] | Ditto, back view, with two views of the sixth molar, right side, upper jaw. |
| [V.] | Fragment of lower jaw, and teeth of Toxodon Platensis. |
| [VI.] | Cervical vertebræ of the Macrauchenia Patachonica. |
| [VII.] | Ditto, ditto, and of Auchenia Llama. |
| [VIII.] | Lumbar vertebræ of the Macrauchenia Patachonica. |
| a. | Medium convex articular surface joining the body of the sacrum. |
| b. b. | Lateral concavities joining the transverse processes of the sacrum. |
| c. | Ossified ligament of an anchylosed lumbar vertebra. |
| [IX.] | Fig. 1 and 2. Fragments of the Scapula. |
| Fig. 3. Distal end of the femur of Macrauchenia Patachonica. | |
| [X.] | Proximal ends of the anchylosed radius and ulna of Macrauchenia Patachonica. |
| [XI.] | Bones of the right fore-foot, Macrauchenia Patachonica. |
| [XII.] | Femur, Macrauchenia Patachonica. |
| [XIII.] | Anchylosed tibia and fibula, Macrauchenia Patachonica. |
| [XIV.] | Right astragalus, Macrauchenia Patachonica. |
| [XV.] | Fig. 1. External metatarsal bone of the right hind-foot. |
| Fig. 2. Proximal end of internal metacarpal bone, right fore-foot. | |
| Fig. 3 and 4. Proximal end of middle metacarpal bone. | |
| Fig. 5. Proximal end of external metacarpal bone, right fore-foot, Macrauchenia Patachonica. | |
| [XVI.] | Fragment of cranium of the Glossotherium. |
| Fig. 1. Side view. | |
| Fig. 2. Base view. | |
| Fig. 3. Inside view, all half natural size. | |
| Fig. 4. Os tympanicum, natural size. | |
| [XVII.] | Fig. 1. Megalonyx Jeffersonii. |
| Fig. 2. Megalonyx laqueatus. | |
| Fig. 3 and 4. Mylodon Harlani. | |
| Fig. 5. Mylodon Darwinii. | |
| [XVIII.] | Lower jaw of the Mylodon Darwinii. |
| [XIX.] | Fig. 1. Side view of the lower jaw. |
| Fig. 2 and 3. Last molar tooth. | |
| Fig. 4. Front view of the symphysis of the lower jaw, Mylodon Darwinii. | |
| [XX.] | Portion of the skeleton of the Scelidotherium leptocephalum. |
| [XXI.] | Fig. 1. Side view of the cranium. |
| Fig. 2. Back view of the cranium. | |
| Fig. 3, 4, and 5, anterior molar, upper jaw Scelidotherium. | |
| [XXII.] | Upper view of the cranium of the Scelidotherium. |
| [XXIII.] | Fig. 1. Inside view of cranium. |
| Fig. 2. Articular surface for the lower jaw. | |
| Fig. 3. Section of upper jaw and molar teeth. | |
| Fig. 4. Section of lower jaw and molar teeth, Scelidotherium. | |
| [XXIV.] | Cervical and anterior dorsal vertebræ of. |
| Fig. 1. Scelidotherium. | |
| Fig. 2. Orycteropus. | |
| Fig. 3. Dasypus. | |
| Fig. 4. Myrmecophaga jubata; all one-third nat. size. | |
| [XXV.] | Fig. 1 and 2. Humerus, radius and ulna of Scelidotherium. |
| Fig. 3. Head of humerus. | |
| Fig. 4. Head of radius. | |
| Fig. 5, 6, and 7. Femur of Scelidotherium. | |
| [XXVI.] | Fig. 1, 3, and 5. Astragalus of Megatherium. |
| Fig. 2, 4, and 6. Astragalus of Scelidotherium. | |
| [XXVII.] | Fig. 1 and 2. Patella and head of tibia of Scelidotherium. |
| Fig. 3, 4, and 5. Ungueal phalanx of Scelidotherium. | |
| [XXVIII.] | Fig. 1. Astragalus of Megatherium. |
| Fig. 2. Astragalus of Scelidotherium. | |
| Fig. 3–6. Astragalus of Mylodon or Megalonyx. | |
| [XXIX.] | Lower jaw of Megalonyx Jeffersonii. |
| [XXX.] | Fragment of the Cranium of Megatherium Cuvieri. |
| [XXXI.] | Section of the upper jaw and teeth of the Megatherium Cuvieri. |
| [XXXII.] | Fig. 1. Magnified view of structure of molar of Megatherium. |
| Fig. 2–5. Ungueal phalanx and portions of tesselated armour of Hoplophorus euphractus. | |
| Fig. 6–11. Jaws and teeth of Ctenomys priscus. | |
| Fig. 12. Bones of right hind-foot of a Rodent. | |
| Fig. 13 and 14. Fossil tooth of a Horse. |
PREFACE.
His Majesty’s ship, Beagle, under the command of Captain FitzRoy, was commissioned in July, 1831, for the purpose of surveying the southern parts of America, and afterwards of circumnavigating the world. In consequence of Captain FitzRoy having expressed a desire that some scientific person should be on board, and having offered to give up part of his own accommodations, I volunteered my services; and through the kindness of the hydrographer, Captain Beaufort, my appointment received the sanction of the Admiralty. I must here, as on all other occasions, take the opportunity of publicly acknowledging with gratitude, the obligation under which I lie to Captain FitzRoy, and to all the Officers on board the Beagle, for their constant assistance in my scientific pursuits, and for their uniform kindness to me throughout the voyage. On my return (October, 1836) to England, I found myself in possession of a large collection of specimens in various branches of natural history; but from the great expense necessary to secure their publication, I was without the means of rendering them generally serviceable.
The Presidents of the Linnean, Zoological, and Geological Societies, having given me their opinion respecting the utility to be derived from publishing these materials, I addressed a letter to the Right Honourable the Chancellor of the Exchequer (T. Spring Rice, Esq.) informing him of the circumstances under which I hoped that I might venture to solicit the aid of Government. In reply, I received a communication (as below) announcing to me that the Lords of the Treasury, from their readiness to promote Science, were willing, under certain conditions, to give me the most liberal assistance.
“Treasury Chambers, August 31, 1837.
“Sir,
“It having been represented to the Lords Commissioners of Her Majesty’s Treasury, from various quarters, that great advantage would be derived to the Science of Natural History, if arrangements could be made for enabling you to publish, in a convenient form, and at a cheap rate, the result of your labours in that branch of science, my Lords will feel themselves justified in giving their sanction to the application of a sum, not exceeding in the whole one thousand pounds, in aid of such a publication; upon the clear and distinct understanding that the Work should be published, and the plates engraved, in such a manner as to be most advantageous to the Public at large, upon a plan of arrangement to be previously submitted to, and sanctioned by the Board, after consultation with those persons, who, from their attainments in this branch of science, are the most capable of advising their Lordships thereupon; and that the payments on account of the said sum of one thousand pounds are to be made to you from time to time, on a certificate that such progress has been made in the engravings, in accordance with the plan previously approved of, as to justify the issue then applied for. My Lords have therefore directed me to communicate to you the views they entertain upon this subject; and to apprize you that they will be prepared to act in conformity with their arrangement, upon learning from you that you are ready to proceed with the Work upon the principles above laid down, and upon receiving from you a statement of the manner in which you think the Work should be published, and the plates engraved, so as most effectually to accomplish the object my Lords have in view, in sanctioning the payment from the Public Funds, in aid of the expenses of the Work in question.
“I remain,
“Sir, Your Obedient Servant,
“A. Y. Spearman.”