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 articulates with the two occipital condyles of the skull.
3. Remove, examine, and draw the 3rd vertebra and note the opisthocœlous centrum, neural arch and neural spine, anterior and posterior zygapophyses, the transverse processes, and the cartilaginous ribs.
[The centrum is procœlous in the Frog and there are no ribs.]
4. Remove and examine the 8th vertebra and note that the centrum is opisthocœlous. Make a drawing of a section showing the centrum.
[In the Frog the centrum is amphicœlous.]
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 transverse 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.]