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CONTENTS. 



GEOLOGICAL INTRODUCTION . . . . . .3 



TOXODON PLATENSIS, Description of Cranium . . . . . . 16 



of Lower Jaw and Teeth . : . . .29 



MACRAUCHENIA PATACHONICA, Cervical Vertebra . . . . 35 



Lumbar Vertebraa . . . .40 



Scapula . . . . 43 



Antibrachium and Fore-foot . . .44 



Femur ..... 48 



Tibia, Astragalus, and Metatarsal Bone . . 50 



GLOSSOTHERIUM, Fragment of Cranium . . . . . . 57 



MYLODON DARWINII, Lower Jaw and Teeth . . . . C 3 



SCELIDOTHERIUM LEPTOCEPHALUM, Cranium and Teeth . . 73 



Vertebral Column . . . .84 



Bones of the Extremities . . . . 88 



MEGALONYX JEFFERSONII, Lower Jaw . . . 99 



MEGATHERIUM CUVIERI, Cranium and Teeth . . . . . 100 



TESSELATED ARMOUR AND BONES, large Edentata . . . 106 



MASTODON ANGUSTIDENS, Cuv. (?) . . . . . . 108 



EQUUS, Molar Teeth ...... 



CTENOMYS PRISCUS, and a large Rodent 



108 



109 



Geological contemporaneity of preceding extinct Mammalia . j 5 



