2. Remove, examine, and draw the 1st or atlas vertebra, note its ring-like 

 form, absence of transverse processes, the concave facets by which it articu- 

 lates with the two occipital condyles of the skull. 



3. Remove, examine, and draw the 3rd vertebra and note the opisthoccelous 

 centrum, neural arch and neura! spine, anterior and posterior zygapophyses, 

 the transverse processes, and the cartilaginous ribs. 



[The centrum is procoelous in the Frog and there are no ribs.] 



4. Remove and examine the 8th vertebra and note that the centrum is 

 opisthoccelous. Make a drawing of a section showing the centrum. 



[In the Frog the centru/m is amphicodous .] 



5. Remove and examine the 9th vertebra or sacrum, and note that the 

 centrum is slightly convex on the anterior surface. The urostyle is fused to 

 the posterior surface of the 9th vertebra. Note also the long flat wing-like 

 trans v T erse processes. 



[In the Frog the centrum is also convex anteriorly and on the posterior surface 

 there are two convex facets for the articulation of the urostyle.] 



34 



