MUSCLES OF CERATODUS 



353 



behind the posterior border of the larynx. The pre-laryngeal 

 region of the oesophagus at this stage is thus 460 fi, the laryngeal 

 region 120 /x, and the post-laryngeal region 140 /x in length. 

 The above can be summed up in the statement that the larynx 



Text-fig. 29. 



Ceralobr. i 



origin of 

 Cleido- branch. 

 cleUkra/n. 



corcvco-scap. 



Embryo 27 mm. Model of Ceratobranchialia, Subarcualis rectus v, 

 Cleido-branchialis, and shoulder-girdle. 



Text-fig. 30. 



cesoph. 



Trans, vent, v 



Sp/i. oesoph. 



et Laryng 



(ventral part) 



trachea. 



Embryo 20 mm. Model showing Transversus ventralis v. and Sphincter 

 oesophagi et laryngis (ventral part) ; the lar\'ngeal muscles are not 

 represented.^ 



^ Text-figs. 28, 29, and 30 were drawn by Miss Cross. 



