444 



THE VERTEBRATE SKELETON. 



not fused together and not presenting any marked peculiarities. 

 In Manatus however there are only six cervical vertebrae and 

 they are very variable. 



In the CETACEA there are invariably seven cervical verte- 

 brae, but they are always very short and are frequently even 

 before birth fused together by their centra into one continuous 

 mass (see fig. 67). Sometimes the last one or two are free. In 

 the Rorquals (Balaenoptera) however, the cervical vertebrae are 



1- 



FIG. 87. CERVICAL VERTEBRAE OF A YOUNG FIN WHALE (Balaenoptera 



musculus) x T V (Camb. Mus.) 

 1. 



surface on the atlas for arti- 

 culation with the occipital 

 condyle of the skull. 



2. foramen for exit of the first 



spinal nerve. 



3. upper transverse process. 



4. lower transverse process. 



In the fresh specimen these two 

 transverse processes are united by 

 cartilage, in adult individuals the 

 whole transverse process is ossified. 



5. epiphyses of centrum. 



6. neural spine. 



quite separate and distinct (fig. 87), and in the fluviatile Odon- 

 toceti, Platanista, Inia, and Pontoporia, and also in Beluga 

 and Monodon, though very short they are free. In Physeter 

 the first vertebra is free while the others are fused. An 

 odontoid process is not commonly present even in Cetaceans 

 with free cervical vertebrae, but a very short one occurs in 

 the Rorquals. The cervical vertebrae of Rorquals give off 

 on each side two transverse processes (fig. 87, 3 and 4) which 



