206 ELEMENTARY BIOLOGY. [XIII. 



e. The two minute passages leading from tlie canal 

 to the outside of the ridge on each side. 



4. The vertebral column as a whole. 



a. Its composition. 



a. Its anterior segmented part formed of the nine 

 vertebrae. 



{3. Its posterior unsegmented part formed by the 

 urostyle and nearly as long as the segmented 

 part. 



b. Its ventral surface. 



a. The solid bony axis formed by the bodies of 

 the vertebrae in front and continued posteriorly 

 by the ventral rounded part of the urostyle. 



^. The transverse processes : their size and direc- 

 tion : those of the second vertebra, slender 

 and directed nearly straight outwards; those 

 of the third and fourth, largest of all and with 

 a distinct inclination backwards : those of the 

 fifth, sixth, seventh and eighth . vertebrae 

 smaller than the rest and directed nearly out- 

 wards ; those of the ninth, very stout, directed 

 outwards upwards and backwards, and having 

 the iliac bones attached to their distal ends. 

 ' The transverse processes arise from their arches 

 closer to the centrum in the second, third and 

 fourth vertebrae than in the others. 



7. The inter-vertebral foramina : the interspaces 

 left between each pair of neural arches, below 

 the level of the zygapophyses. 



