VEETEBRATA. 89 



h. Dentary, the lower jaw. 



c. Vomer, the bone bearing teeth in the roof of the 



mouth. 



d. Cranium, the brain-case. 



e. Occipital foramen, an opening in the posterior end 



of the cranium. What is it for ? 

 /. Orbits, the eye sockets. 



3. The Vertebral Column. 



a. Vertebrae, the small bones which make up the 



vertebral column. How many vertebrae are 

 there ? 



h. Urostyle, the blade-like bone at the end of the 

 vertebral column. 



c. Sacrum, the vertebra to Avhich the posterior ap- 



pendicular skeleton is attached. 



d. Atlas, the first vertebra. How does it differ from 



the rest? 



4. A Vertebra. (Use a vertebra from the skeleton of 



some mammal for comparison.) 



a. Centrum, the ventral cylindrical portion of a 



vertebra. 



b. Neural arch, the arch of bones dorsal to the 



centrum. What does it enclose ? 



c. Neural spine, a dorsal projection of the arch. 



d. Lateral spines, the paired lateral projections. Are 



ribs present? Sketch a vertebra. 

 Why is the vertebral column made up of such a 

 series of small bones ? 



5. The Pectoral Girdle. 



The pectoral girdle is the girdle of bones to which 

 the fore limbs are attached. It consists of a series 

 of bones which nearly encircle the body. 



a. Sternum, the "breast-bone." 



