go VERTEBRATE ZOOLOGY 



the thoracolumbar in size and form ; its transverse processes are, 

 however, somewhat larger and its ribs longer than those of the 

 other vertebrae, and the distal ends of the ribs articulate with the 

 pelvic girdle. The caudal vertebrae vary much in form and size. 

 The first two or three are similar to those of the thoracolumbar 

 region, but are smaller, with the transverse processes much less de- 

 veloped and usually without ribs. From about the twenty-third 

 vertebra a ventral or haemal arch, in which the caudal vein and 

 artery lie, characterizes the ventral side of the vertebra. 



The ribs are small, rather irregular rods of bone which are 

 bifurcated at their proximal ends. 



Exercise 25. Draw three views, on a scale of 2 or 3, of one of the 

 thoracolumbar vertebrae and the ribs belonging to it, — an an- 

 terior view, a side view, and a ventral view. 



Exercise 26. Draw the anterior end of the atlas on a scale of 2 or 3. 



Exercise 27. Draw an anterior and also a side view of the twenty- 

 fourth vertebra on a scale of 2 or 3. 



