In preparing the preceding account of the cervical and lumbar regions of the vertebral column of the Macrauchene, I have felt frequently a strong desire to enter into a comparison between them and the corresponding vertebræ of the extinct Pachyderms of the Paris Basin. Some of these, as the _Anoplotherium gracile_, in the length and slenderness of the cervical vertebræ, resemble both _Auchenia_ and _Macrauchenia_; others, as the _Palæotherium minus_, and probably the rest of the genus, resemble the _Camelidæ_ and _Macrauchenia_ in having seven lumbar vertebræ. Cuvier points out the resemblance which the atlas of the Anoplothere bears to that of the Camel, and especially of the Llama;[20] but he expressly notices the existence of the canals for the vertebral artery in the fifth or sixth cervical vertebra of the _Anoplotherium commune_.[21] Do the cervical vertebræ—say from the third to the sixth inclusive—of the _Palæotherium_ present an imperforate condition of their transverse processes, or exterior part of their sides? Cuvier, who seems not to have been aware of this peculiarity in the _Camelidæ_, merely notices the absence of these arterial foramina in the last cervical vertebra of the _Palæotherium minus_,[22] which, unfortunately for the comparison I am desirous of establishing, is that which most commonly presents this imperforate condition in the Mammalia generally. As, however, the cervical vertebræ of the Palæothere had the anterior articular surface of the body convex, and the transverse processes produced into descending laminæ, it is most probable that they corresponded with the cervical vertebræ of the typical Pachyderms in the condition of their arterial foramina. The sacrum and ossa innominata in the present specimen of _Macrauchenia_ are very imperfect; but sufficient is preserved to show that the sacrum was anchylosed to the ilia: the lower boundary of this anchylosis is marked below by an external ridge, and by vascular canals and grooves in the substance of the bone, as in the Hippopotamus. The body of the sacrum is lost, but the smooth articular convexities upon the transverse processes adapted to the articular depressions of the last lumbar vertebra are fortunately preserved.