80 



University of California Publications in Zoology 



atlas 



intercentra 



sternum 



sternal ribs 



postxiphisternal ribs 



cervical ribs 



xiphisternal ribs 



sacrum 



FIG. 39. Presacral and sacral vertebrae and ribs oi Dipsosaurus dor salts in ventral view. The drawing is 

 a composite. 



rarely on the fourth) and ending on the eighth. The bony portions of the first two cervical 

 rib pairs are short, while the second two are much longer, about the same length as the 

 anterior thoracic ribs. The next four (rarely three) rib pairs, on presacral vertebrae nine 

 through twelve, are sternal ribs, attached ventromedially to the lateral borders of the 

 sternum through their cartilaginous ventral portions. Two (rarely three; sometimes one in 

 Sauromalus) pairs of xiphisternal ribs follow the sternal ribs. These ribs articulate dorsally 



