130 BULLETIN UNITED STATES GEOLOGICAL SUKVEY. [Fo?.VL 



middle of the neck the anterior entrance of the vertebral canal are 

 ellipses placed vertically. They become more circular as we ajjproach 

 the thoracic end of the chain. On the eighth vertebra, mesially, and" 

 beneath anteriorly, we find, bounded on either side by the parapophysial 

 processes, the commencement of the interhyapophysial groove or canal 

 for the carotid artery. It extends through the fourth vertebra with 

 about an equal amount of distinctness and depth. (For names of parts, 

 see Explanation of Plates at the end of this paper.) 



It will be seen that the carotid in this Lark is single, and bifurcate at 

 a point about opposite the third cervical vertebra, the branches pursuing 

 their usual courses above. 



A neural spine is feebly developed upon the axis posteriorly, this 

 process becoming more strongly marked on the summits of the next 

 three succeeding vertebrae, the remainder of the cervical segments being 

 devoid of this feature, though we hav^e occasionally found an evident 

 attempt at its reproduction in the ultimate cervical. The nethermost 

 portion of the pseudo-centrum of the first vertebra has been considered 

 to be the atlantal hypapophysis Be this as it may, the hypapophysis 

 of the axis certainly has a much greater claim to be termed a process, 

 while on the third and fourth segments this spine constitutes one of 

 the most marked features of the vertebra, being a longitudinal and quad- 

 rate lamina of bone, equally well developed on the two vertebrae in ques- 

 tion, directed immediately forward. In the case of Ihe fifth cervical, the 

 hypapophysis has again degenerated to a minute median i3oint, to be 

 entirely obliterated from the sixth. At the ninth it again makes its 

 appearance as a delicate and flattened plate at the anterior margin of 

 the vertebra beneath, at the point at which in the carotid canal it is first 

 seen in the eighth. In the remaining ones it is prominently developed 

 and directed forwards from the median plane in each vertebra as a quad- 

 rate lamina. It is usually triplicate in the last, but does not arise from 

 a common stem, as in other birds. 



Parapophysial processes appear as lateral spines first on the third 

 cervical; in the middle of the series they are very long and delicate, 

 being parallel with the centrum of the vertebra to which they belong. 

 They become markedly suppressed near the termination of this division 

 of the spinal column. 



Anterior and posterior zygapophyses retain throughout the cervical 

 vertebrae their most common ornithic features 5 in the middle of the 

 neck the postzygapoiDhysial processes are long and bent slightly towards 

 the neural canal, leaving quite an extensive lozenge-shaped space be- 

 tween them in this region where the cord is unprotected by bone ; the 

 interarticular facets among the centra likewise retain their most com- 

 mon avian characteristics. The bodies for the most part seem to be 

 slightly compressed from side to side, with a faint inferior median crest. 

 The fourth vertebra has a delicate and outwardly arched interzygapo- 

 physial bar, that includes within it an elliptical foramen on each side of 



