IV.] RODENTIA, 33 



each vertebra bears at its hinder end a pair of hypapophysial 

 tubercles. 



In the Chiroptera all the cervical vertebrae are broad, 

 very short from before backwards, with slender neural arches 

 from which (except in the axis) no distinct spinous processes 

 are developed. In certain forms (as Vespei-ugo) some of the 

 vertebrae have distinct double hypapophysial spines project- 

 ing backwards. 



In the RoDENTiA the atlas has usually broad, moderately 

 long, wing-like transverse processes. The odontoid process 

 is long and slender; the spinous process of the axis is much 

 developed, while as a rule that of the other cervical vertebras 

 is exceedingly small. The transverse processes of the fifth 

 and sixth have large inferior lamellae ; that of the seventh 

 is sometimes perforated at the base (as in Lepiis), and 

 sometimes imperforate (as in Hydroch(C7'us). 



In the Capybara [Hydrochcerus) and some others, the side 

 of the arch of the atlas is perforated near its anterior border 

 for the exit of the first spinal (sub-occipital) nerve, and also 

 near its hinder border for the second cervical nerve. 



In the Jerboas {Dipus) a very exceptional condition of 

 the cervical vertebrae occurs. The atlas is free, but all the 

 others are ankylosed together by both bodies and arches, 

 and the bodies are very wide and depressed, as in the 

 Armadillos. 



Among the Ungulata, the atlas (Fig. 13) in the Peco?'a is 

 very long, with deep articular cavities for the occipital con- 

 dyles. The transverse processes are not wide, but much 

 extended from before backwards, and flattened from above 

 downwards. Each is perforated by a foramen {sn') \\ hich gives 

 exit to the inferior division of the first cervical nerve, but not 

 by the vertebral artery, which usually enters the neural canal 

 between the arches of the second and third vertebi^e. The 



D 



