OUR FACE FROM FISH TO MAN 



el's cartilage), with certain connecting bars (hyo- 

 mandibular, ceratohyal) that tie the jaws on to the 

 braincase. 



These jaw cartilages resemble the bars of 

 cartilage (I-V) that form the supporting frame- 

 work for the gills. 



^and flf 



fflUic^ 



letr/nxsujJ 



ouadrate 





musc/e constnctormuscles 



Fig. 8. Jaw Muscles of Shark, Showing the Essential Similarity 



OF the Jaw Muscles to the Constrictors of 



THE Branchial Arches. 



For details, see p. xiv. 



Even the jaw muscles appear to be modified 



gill-arch muscles. The principal jaw muscles 



(Fig. 8) are simply bands or sheets of muscle 



wrapped around the angular bend where the upper 



and lower jaw segments articulate with each other. 



The lower jaw is pulled downward chiefly by a 



backward pull of the horizontal muscles. 



18 



