14 THE NECTURUS 



VERTEBRA 



Twelfth Vertebra 



Mdke a sagittal section through this vertebra. 



Drawing 5. Make a drawing of the section showing the hourglass 

 shape of the centrum and the relation of the centrum to the other 

 structures of the vertebra. 



Note the following parts: prezygapophysis postzygapo- 

 physis, neural arch, neural spine, transverse process, para- 

 pophysis and diapophysis. Is the vertebra procoelus, 

 amphicoelus or opisthocoelus? Note the short rib attached 

 to the transverse process by the two heads. On what 

 vertebrae are the ribs found? Number them. 



Twenty Fifth Vertebra (Caudal) 

 Note the shape of this vertebra in longisection. 

 Drawing 6. Make a drawing from the anterior face. 



Note the development of the haemal arch and spine. 

 On what vertebrae numbering from the head posteriorly, 

 are haemal arches found ? Why do these arches not appear 

 earlier in the series? 



Sacral Vertebra 



Is there any structural differences between this vertebra 

 and the rest of the series ? 



RIBS 



The ribs in the amphibia are short and not connected 

 with any ventral structures. Note the two heads of the 

 rib, a tubercular and a capitular. With what processes do 

 they articulate? On what vertebrae by number, are ribs 

 found ? 



