CE K VIC A L VER TEBR&. 



[CHAP. 



and as ossification takes place gradually from within out- 

 wards, and does not reach the outer extremity until the 

 animal approaches maturity, specimens are frequently met 

 with in museums, which, instead of completely annular 

 transverse processes, show only truncated upper and lower 

 bars. In some species, however (as in Megaptera boops], 

 most of the cervical vertebras remain permanently in this 

 condition. 



az 



FIG. 18. Anterior surface of fourth cervical vertebra of the same animal, T \. as ante- 

 rior of zygapophysis ; t upper transverse process ; t' lower transverse process. 



Among the Odontoceti, ail the cervical vertebrae are free in 

 the Gangetic Dolphin (Platanistd), and in the allied South 

 American genera Inia and Pontoporia, also in the Nar- 

 whal (Monodon) and the Beluga, or the White Whale. In 

 most of these genera the atlas has a large hypapophysial 

 process, projecting under and articulating with the body of 

 the axis, which develops no distinct odontoid. In the 

 Narwhal irregular ankyloses between the bodies of the cervical 

 vertebrae are very frequent. In all the other Delphinida 

 (including Delphinus, Orca, Pseudorca, Globicephalus, PJio- 

 ccena, &c.), at least the first and second cervical vertebrae 

 are united by both body and spine, and most commonly 

 some of the succeeding vertebrae are joined to them. If 

 any are free, it is always those situated most posteriorly, 

 and they have extremely thin, sub-circular disk-like bodies, 



