SitEleton of CETACEA. 417 



phjsis begins to project from the fore part of the diapophysis of 

 the third dorsal, increases in length to the fonrth, and is gradually 

 transferred in the sixth and seventh dorsals to the outer side of 

 the prozygapophyses : in the following vertebrae it seems to take 

 their place, and to occasion a reversing of the usual relative posi- 

 tion of the zygapophyses ; for whereas in the cervical and 

 anterior dorsal vertebrae the anterior ones are overlapped, as in 

 other Mammals, by the posterior zygapophyses of antecedent 

 vertebrae,- — in the succeeding dorsals, beginning with the seventh, 

 the posterior zygapophyses seem to be overlapped and con- 

 cealed by the anterior ones ; but the appearance is due to the 

 place of the zygapophyses being taken by the metapophyses.^ 

 These latter processes, in fact, continue after the articular surface 

 has ceased to be developed, and after the entire disappearance of 

 the posterior zygapophyses, to project forward from the thirteenth 

 dorsal to the sixth lumbar vertebra; inclusive ; beyond which the 

 neural arch is devoid of all exogenous processes, save the spine, s, 

 until the middle caudal vertebras, where rudiments of the meta- 

 pophyses again reappear. There are no anapophyses in the 

 Cetacea. 



The four anterior ribs have a head and neck : the rest are sus- 

 pended by the homologue of the tubercle to the end of the trans- 

 verse process. The costal cartilages are partially ossified : the 

 first four pairs articulate ivith the sternum : the original separations 

 of the parts of that bone have disappeared. The first piece or manu- 

 brium has an anterior median notch and two broad lateral processes. 



In DelpJihius delphis, of the seven cervical vertebras the first 

 two have become anchylosed together : there are sixty-three other 

 vertebra), of which the first fifteen bear moveable ribs; thirty- 

 three vertebra) have transverse processes without ribs : the forty- 

 second vertebra from the skull begins to support ha3mapophyses : 

 the eight terminal vertebra) consist of the centrum only, and 

 are much flattened. The metapophysis begins abruptly, as a 

 long well-marked process, from the fore part of the diapophysis 

 of the fourth dorsal, progressively approximates and attains the 

 outside of the prozygapophysis in the eighth dorsal, performs the 

 function of an articular process as far as the sixth lumbar, clamp- 

 ing, as it were, the sides of the back part of the base of the spine 

 of the antecedent vertebra, disappears in the next dozen lumbar 

 vertebra), and reappears in the caudal vertebra) at the fore part 

 of the base of the spine. The six anterior i)airs of ribs support 

 hasmapophyses which unite directly with the sternum. 



' XLiv. No^e, vol, ii, p. 452. 

 VOL. II. E E 



