219 



open into the canal for the spinal chord ; this structure is peculiar to 

 the Camel tribe amongst existing Mammalia. 



Presented by Professor Owen, F.R.S. 



925 2 . The third cervical vertebra of a Llama vertically and longitudinally bi- 

 sected, to show more closely the position and extent of the canals for the 

 vertebral arteries. Presented by Professor Owen, F.R.S. 



Both of the cervical vertebrae of the Macrauchenia are of the same 

 size ; each measures seven inches and a half in extreme length, three 

 inches and a half in breadth, and four inches in depth. 



In the Giraffe and the Camel-tribe the spinous processes are thin 

 lamina; of considerable extent in the axis of the vertebra, but rising to a 

 very short distance above the level of the vertebral arch : the spinous 

 processes have the same form in the corresponding vertebrae of the 

 Macrauchenia, but present a still greater longitudinal extent : they com- 

 mence at the interspace of the anterior oblique processes and extend to 

 opposite the base of the posterior oblique processes ; the upper margin 

 describing a gentle curve. The transverse processes also present the 

 form of slightly produced, but longitudinally extended, laminae : their 

 disposition is essentially the same as in the Ca?nelidce, but more nearly 

 corresponds with the modifications presented by the Auchenias, or South 

 American species. The inferior transverse processes — the only ones 

 that are developed in fishes, But which are present in the cervical vertebrae 

 in Mammals — are continued in the Macrauchenia, from the sides 

 of the under surface of the anterior part of the body of the vertebra ; 

 their extremities being broken off, it cannot be determined from the 

 present specimens how far they extended from the body of the vertebrae, 

 but they gradually subside as they pass backwards : the superior transverse 

 processes are continued outwards from the sides of the posterior part of 

 the body of the vertebrae, and gradually subside as they advance along 

 three-fourths of the body of the vertebra : they are not continued into the 

 anterior and inferior transverse processes, as in the Llama and Vicugna, but 

 are separated therefrom by a narrow and shallow groove. The articular or 

 oblique processes closely resemble those of the Llama in form and in the 



2 f2 



