221 



The long vertebral or spinal canal is slightly expanded in the 

 present fossils at the two extremities ; this expansion, which is generally 

 in the ratio of the extent of motion of the vertebrae on each other, is 

 more marked in the Camel, where the form and mode of articulation of 

 the bodies of the vertebrae are designed to admit of a free and extensive 

 inflection of the cervical vertebrae ; such as is exemplified in the sigmoid 

 flexure of the neck in the living animal. In the Aucheniae, on the con- 

 trary, the neck is less gracefully carried erect and in an almost straight 

 line, and the form of the vertebrae and the nature of their joints corre- 

 spond to this condition. From the length of the bodies of the cervical 

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

 anterior and posterior articular surfaces, it may be inferred that the long 

 neck of this singular extinct quadruped was carried in the same stiff and 

 upright position as in the Llama and Vicugna. 



The following individual differences are observable in the two cervical 

 vertebra; of the Macrauchenia : — in the posterior one, No. 925, the supe- 

 rior arch is wider and with thicker parietes, the body is more concave 

 below, and the inferior transverse processes have a more lengthened 

 origin. 



926. The fractured body of the first lumbar vertebra of the Macrauchenia pa- 



tachonica : the floor of the spinal canal is traversed by a strong median 

 longitudinal eminence. 



From the tertiary deposits of Port St. Julian, Patagonia. 



Presented by Charles Darwin, Esq., F.R.S. 



927. A fractured body of the second lumbar vertebra of the Macrauchenia 

 patachonica : the longitudinal eminence on the floor of the spinal canal 

 is less developed in this specimen. 



From the tertiary deposits of Port St. Julian, Patagonia. 



Presented by Charles Darwin, Esq., F.R.S. 

 92S. A fractured body of the third lumbar vertebra of the Macrauchenia 

 patachonica ; it is much compressed and reduced to a ridge along the 

 middle of its under surface. 



From the tertiary deposits of Port St. Julian, Patagonia. 



Presented by Charles Darwin, Esq., F.R.S. 



