290 THE SKELETON OE THE BABBIT. 



c, The remaining cervical vertebrae:— third to seventh. 



i. The centra are short, broad from side to side, 

 thin from above downwards, and obliquely 

 truncated at the ends. The centrum of the 

 seventh vertebra bears at its posterior end a 

 pair of facets, which form parts of the articu- 

 lar surfaces for the heads of the first pair of 

 thoracic ribs. 



ii. The neural spines are small, excepting that of 

 the seventh vertebra. 



iii. The transverse processes are perforated at their 

 bases by the vertebrarterial canals : beyond 

 these they divide into dorsal and ventral por- 

 tions, of which the latter, the inferior lamellae, 

 form prominent bony plates, except in the 

 seventh vertebra, from which they are absent. 



iv. The zygapophyses are borne on the sides of the 

 neural arches ; the anterior facing upwards 

 and inwards, the posterior downwards and 

 slightly' outwards. 



3. The thoracic vertebrae. 



These are usually twelve, sometimes thirteen, in 

 number, and are characterised by bearing movably 

 articulated ribs. The neural spines are long, 

 especially in front : that of the tenth or anticlinal 

 vertebra is nearly vertical, those in front of it 

 sloping backwards, and those behind forwards. The 

 posterior two or three thoracic vertebrse are larger 

 than the others, and gradually approach the lumbar 

 vertebrae in size and shape. 



a. A typical thoracic vertebra :— any one of the first 



six. 



i. The centrum is short, and thick from above 



downwards. On each side in front is a small 



facet, which, with a similar one on the hinder 



edge of the vertebra next in front, forms the 



