THE SKELETON IN MAMMALIA. VERTEBRAL COLUMN. 449 



Procavia sometimes has thirty thoraco-lumbar vertebrae, a 

 greater number than occurs in any other terrestrial mammal ; 



FIG. 89. 



1. neural spine. 



2. neural canal. 



3. prezygapophysis. 



4. facet for articulation with the 



tuberculum of the rib. 



FlEST AND SECOND THORACIC VERTEBRAE OF AN Ox (BOS 



taunts) x . (Camb. Mus. ) 



5. facet for articulation with the 



capitulum of the rib. 



6. postzygapophysis. 



7. foramen for exit of spinal 



nerve. 



twenty-two of these are thoracic and eight lumbar. In Phe- 

 nacodus the convergence of the neural spines to a centre of 

 motion is well seen. 



In the Proboscidea there are twenty-three thoraco-lumbar 

 vertebrae, of which nineteen or twenty bear ribs. 



In the RODKNTIA there are generally nineteen thoraco- 

 lumbar vertebrae but occasionally the number rises as high as 

 twenty-five. In the Hares (Leporidae) the number is nineteen, 

 R. 29 



