xiii.] THE FROG. 215 



b. Its ventral surface. 



a. The solid bony axis formed by the bodies 

 of the vertebrae in front and continued pos- 

 teriorly by the ventral rounded part of the 

 urostyle. 



/3. 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. 



y. The inter-vertebral foramina : the interspaces 

 left between each pair of neural arches, below 

 the level of the zygapophyses. 



c. The dorsal surface of the spinal column. 



a. The ridge down its middle formed by the row 

 of spinous processes, and continued behind 

 by the dorsal ridge of the urostyle. 



P. The lateral prominences caused by the ar- 

 ticular processes : the articulations between 

 the anterior articular processes of one verte- 

 bra, and the corresponding posterior processes 

 of its predecessor. 



y. The spaces left between the dorsal part of 



