THE PHARYNX. 



401 



day (Fig. 161) the maxillary. MX, mandibular, MX, hyoid, HY. 

 and first branchial arches form conspicuous ridge-like projections 



. 



in the side walls of the pharyngeal region. Of the branchial 

 grooves, or external depressions separating the successive arches, 



D D 



