12 THE VOYAGE OF H.M.S. CHALLENGER. 



diverge from one another opposite the fourth cervical vertebra. The number of cervical 

 vertebras destitute of hypapophyses, therefore, indicates the extent of the vertebral 

 column with which these arteries are in contact. 



The variations in respect of the bodies of the cervical vertebrae in different species are 

 few and unimportant. 



In Eudyjytes chrysolo2^hns, Spheniscus demersus, Spheniscus magellaniciis, SpTieniscus 

 mendiculus, Pygosceles tcBniatus, and Aptenodytes longirostris the fourth cervical vertebra 

 develops a hypapophysis in adtlition to those met with in Eudyptcs chrysocome from 

 Tristan d'Acunha. In Eudyptes chrysocome from Kerguelen an additional hy25apophysis 

 is developed on the ninth cervical vertebra, while in Aptenodytes, on the other hand, the 

 hypapophysis of the tenth cervical vertebra met with in Eudijptes chrysocome is want- 

 ing. In every species of the genus Spheniscus the hypapophyses of the lower cervical 

 vertebrae are relatively larger than in those of any other genus. 



The transverse p)rocesses of the cervical vertebrae consist as usual of two bars, an 

 anterior and a posterior, which unite together to complete the foramen for the vertebral 

 artery. The canal formed by the apposition of the different vertebrae for the reception of 

 that artery extends from the third to the thirteenth cervical vertebra, but is absent at 

 the anterior portion of the neck, where, by reason of both atlas and axis being destitute 

 of any transverse process, and consequently of a vertebrarterial foramen, the canal is 

 deficient. The free extremities of the posterior bars form a series of small, rounded, and 

 but slightly projecting nodules from the fourth to the tenth cervical vertebra. In the 

 eleventh, twelfth, and thirteenth vertebrae, on the other hand, these nodules are largely 

 developed, and assume the appearance characteristic of the transverse processes of the dorsal 

 region. Those of the eleventh and twelfth vertebrae are rather smaller than those of the 

 thirteenth, which indeed are of larger size, and more prominent than the transverse pro- 

 cesses of any other vertebrae, not excepting those of the dorsal region. Above the fourth 

 vertebra they are scarcely distinguishable. The anterior bars of the cervical transverse 

 processes (cervical ribs) are provided with elongated spines which afford attachment 

 to the tendons of insertion of the longi colli muscles. These spines are well developed 

 from the third to the eleventh cervical vertebra inclusive. In the first and second, by 

 reason of the absence of a transverse process, they are absent, while in the twelfth and 

 thirteenth, although present, they are thicker, shorter, and less projecting than in the 

 vertebrae higher up. 



With respect to the variations in the transverse processes, I find that while in all 

 three specimens of Eudyptes chrysocome, the nodular extremities of the posterior bars of 

 the cervical transverse processes are distinctly visible from the fourth to the thirteenth 

 vertebra, in every other species, including Eudyptes chrysolophus, they are entirely absent 

 in the upper five cervical vertebrae, and only make their appearance from the sixth to the 

 thirteenth vertebra inclusive. 



In every species of Spheniscus, with the single exception of Spheniscus minor, the 



