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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Nov. 21, 



Perissodactyla ; and with an astragalus which, in the apparent entire 

 absence of any facet for the cuboid, is, I may affirm, more Perisso- 

 dactyle than that of any member of the order, except Hyrax. 



None of the older Tertiary mammalia can produce such strong 

 claims to be considered an example of what has been termed " a 

 generalized type" as Macrauchenia ; and yet there seems little doubt 

 that the latter is the South American equivalent, in point of age, of 

 our Irish Elk ! 



Again, Macrauchenia, alone, affords a sufficient refutation of the 

 doctrine, that an extinct animal can be safely and certainly restored 

 if we know a single important bone or tooth. If, up to this time, 

 the cervical vertebrae of Macrauchenia only had been known, palaeon- 

 tologists would have been justified by all the canons of comparative 

 anatomy in concluding that the rest of its organization was Came- 

 lidan. With our present knowledge (leaving Macrauchenia aside), a 

 cervical vertebra with elongated centrum, flattened articular ends, 

 an internal vertebral canal, and imperforate transverse processes, as 

 definitely characterizes one of the Camel tribe as the marsupial bones 

 do a Marsupial, — and, indeed, better; for we know of recent non-mar- 

 supial animals with marsupial bones. Had, therefore, a block contain- 

 ing an entire skeleton of Macrauchenia, but showing only these por- 

 tions of one of the cervical vertebrae, been placed before an anatomist, 

 he would have been as fully justified in predicting cannon-bones, 

 bi-trochanterian femora, and astragali with two, subequal, scapho- 

 cuboidal facets, as Cuvier was in reasoning from the inflected angle 

 of the jaw to the marsupial bones of his famous Opossum. But, for 

 all that, our hypothetical anatomist would have been wrong ; and, 

 instead of finding what he sought, he would have learned a lesson 

 of caution, of great service to his future progress. 



EXPLANATION OF PLATE VI. 



Fig. 1. Cervical vertebra of Macrauchenia Boliviensis, Huxley; restored from 

 the opposite side, posteriorly. 

 1 a. The same vertebra, viewed from in front. 



1 b. The same vertebra, viewed from behind. 



2. Astragalus (left), from above. 



2 a. „ „ from below. 



2 b. „ „ from the outer side. 



3. Fragment of the occipital portion of the cranium, restored in outline. 



3 a. The same fragment, viewed from without and laterally. 



4. Part of the upper jaw and palate, and lateral view (a) of the crown of the 



most perfect tooth. 



4 a. Side-view of the large fragment of the matrix containing the teeth, with 



the smaller fragment, exhibiting the coronal impressions, adapted to it. 



