62 NEW YORK STATE MUSEUM 



lateral wall is perforated on either side by a small foramen. The 

 parapophysial spines extend backward as far as the posterior artic- 

 ular facet, and the hypapophysis is in the middle of the body of the 

 vertebra. 



In the jth vertebra the neural spine still maintains its position as 

 in the last segment, but is rapidly disappearing. The facings of 

 the articular surfaces on the zygapophysial processes are more de- 

 cided, while those on the posterior pair are borne on projecting 

 and diverging limbs of considerable length. The delicate bar that 

 connected them on either side, in the 4th vertebra, is here de- 

 ficient at the middles. Other features are but slightly modified ; the 

 hypapophysis has assumed a position just behind the anterior 

 articular surface of the body. 



The neural spine of the 6th vertebra is barely perceptible, and the 

 interzygapophysial bar is again intact as a delicate bridge. At the 

 base of each postzygapophysis above, a little projection is seen, 

 which occurs on the four succeeding segments ; both then are 

 obliterated. 



The vertebral canals have the form of a vertical ellipse, and the 

 parapophysial spines are again shortening. Beneath, we observe 

 that the hypapophysis has disappeared, and at its site, in the last 

 vertebra, the carotid canal begins to form. The body of this 

 vertebra is nearly square on transverse section. But slight modifi- 

 cation has taken place in the /th vertebra. The limbs of the 

 postzygapophyses are shorter ; the connecting bar is still intact ; the 

 neural spine has entirely disappeared ; and the carotid canal is 

 deeper and narrower. 



In the 8th vertebra the interzygapophysial bar is once more in- 

 complete, while the changes taking place in the last vertebra are be- 

 coming better marked. 



Sharp lateral processes form the walls of the narrow carotid 

 canal in the gth vertebra, and the vertel^ral canals are nearly circular 

 and increasing in caliber. The parapophysial spines are nearly as 

 long as the body, while the vertebrae are now beginning to be shorter 

 and heavier. The anterior pair of articular facets look upward 

 and inward, the reverse being the case with the hinder pair. A 

 tuberous neural spine and hypapophysis make their appearance in 

 the loth vertebra, the latter being in the middle of the body. Para- 

 pophysial processes are shorter, though more pronounced, while the 

 carotid canal has ceased to exist. The general fonn of this verte- 

 bra is cubical. 



