BY W. J. McKAY. 923 



rounded than in the case of the atlas. There is a weakly devel- 

 oped anterior zjgapophysis and a well developed posterior one. A 

 short recurved spike of bone, springing from the transverse process , 

 is in serial homology with the ribs. The anterior surfaces of the 

 laminae are not formed into a zygosphene, but there is a zygantrum 

 developed posteriorly. The hypapophysis presents a reduplicated 

 arrangement, for closely united to the hypapophysis of the atlas 

 is seen a small process of bone separated by a suture from the 

 odontoid above. This is followed immediately by a well marked 

 recurved spine, the true hypapophysis. The anterior of the two 

 processes appears in all the snakes examined, and is also well 

 developed in Grammatojyhora ; while in the atlas of man a well 

 marked nodule of bone may be sometimes observed in this situation. 

 The third vertebra was remarkable in having no ribs attached to 

 it ; a small process of bone, anchylosed to the transverse process, 

 being the only representative of a rib. 



On considering the spinal column as a whole, we find that it is 

 composed of two pyramids placed with their bases opposed to one 

 another. In this it agrees with the observations of M. Roche- 

 brune, who says, after examining a great number of skeletons of 

 snakes, " On observe que I'axe osseux est forme de deux pyra- 

 mides etroites sensiblement pentagonales, oppos6es par leur base 

 la plus large, plus au moins longues en raison des os qu'elles 

 renferment, et dont la premiere depasse rarement les trois 

 huitiemes de la longueur totale du corps." The vertebrae number 

 about 175; the exact number is difficult to ascertain, since the 

 last fifteen are but thin leaves of bone. Of this number 124 

 vertebrae bear ribs. 



The only points to be noted in connection with the first ten 

 vertebrae are that they are relatively small, and that the neural 

 spine, instead of springing from the whole line of junction of the 

 laminae, arises from the posterior portion only, and running 

 upwards is constricted so that it appears somewhat hour-glass 

 shaped when viewed from the side. 



The hypapophysis is also longer and less oblique, and at the 

 same time weaker than it is more posteriorly. Gradually, as we 



