40 



ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 





cervical vertebrae of the Macrauchenia, and the almost flattened form of their 

 anterior and posterior articular surfaces, I infer that the long neck in this singular 

 quadruped must have been carried in the same stiff and upright position as in 



the Vicugna and Guanaco. 



The following individual differences are observable in the two cervical verte- 

 brae of the Macrauchenia ; — in the posterior one the superior arch is wider and 

 with thicker parietes, the body is more concave below, and the inferior transverse 

 processes have a more lengthened origin. 



Not a fragment of dorsal vertebra, ribs or sternum, is included in the col- 

 lection of the bones of the Macrauchenia ; but fortunately seven lumbar verte- 

 brae, forming a consecutive series of the same individual as that to which the 

 cervical vertebrae belonged, were obtained, all more or less fractured, but all 

 sufficiently perfect to demonstrate their true nature. These vertebrae, although 

 not possessing such distinctive characters as the cervical, contribute by no means 

 an unimportant element towards the illustration of the osteology of the Macrau- 

 chenia, and support the view which I have taken of its affinities ; for, although, as 

 will be seen from the structure of its extremities, this animal must be referred to 

 the Order Pachydermata, yet no existing species of that order has more than 

 six lumbar vertebrae ; whilst among the Ruminants it is only in the Camel, Dro- 

 medary, Llama and Vicugna, that the lumbar vertebrae reach the number seven,— 

 the same number which characterizes the extinct annectant species in question. 

 The dimensions of the vertebrae in the Macrauchenia present the same relations to 

 the two cervical vertebrae above described, which the lumbar vertebrae of the 

 Vicugna bear to the third, fourth, or fifth of its cervical vertebrae. But here we 

 begin to discover modifications of form, in which the Macrauchenia deviates from 

 the Camelidae, and approaches the Pachyderms, as the Horse and Hippopotamus ; 

 and these indications become stronger as the vertebrae approach the sacrum. 



In the Camel, as well as in the Horse and Hippopotamus, the bodies of the 

 lumbar vertebrae diminish in vertical extent, or become flatter, as they approach 

 the sacrum; but this character is more strongly marked in the Macrauchenia than 

 in either of the above species. But in the Camelidae the transverse processes of 

 the lumbar vertebrae, are elongated, flattened, and narrow, resembling ribs, except 

 that they are nearly straight ; and this is more particularly the case with the 

 transverse processes of the last lumbar vertebrae, which are the narrowest of all 

 in proportion to their length, and stand freely out without touching the sacrum. 

 The transverse processes of the lumbar vertebrae of the Giraffe resemble those of 

 the Camel, but are relatively smaller and shorter. In the Hippopotamus the 

 transverse processes of the lumbar vertebrae are much broader in proportion to 

 their length than in any of the Ruminants, and they increase in breadth to the 



