19 



becomes applied the quadrate cartilage which bears the lower jaw or 

 Meckel's cartilage. To the posterior surface of the hyomandibular 

 near the otic region of the primordial cranium is attached the stylo- 

 hyal bearing the ceratohyal (Fig. 2). Later the pterygoid process 



Pterotic Region 



Sty. hy. 



Ce. hy. '' 



Qu. 

 Fig. 2. Gobius capito at time of hatching. 



Mck. 



grows out from the quadrate. The quadrate fuses with the hyomandi- 

 bular and the latter becomes broad and sends out posteriorly the 

 opercular process which comes to bear the operculum while the stylo- 

 hyal attachment is shifted lower down. After this stage the bones 

 become laid on and a condition represented by Parker in Fig. Vn 

 and VIII PI. V is attained. 



The cartilages at this stage in a young Silurus are represented 

 in the accompanying diagram (Fig. 3) constructed from a model. The 

 hyomandibular articulates with the otic region of the skull below the 

 pterotic ridge by a long articulation. From this region it narrows 

 downwards to a certain level at which in front the hyomandibular 

 nerve passes out in a notch while behind is attached the opercular 

 cartilage which supports the operculum. Thence the cartilage broa- 

 dens downwards and forwards to the quadrate and symplectic region. 

 At the posterior ventral angle, that is, the symplectic region the 



2* 



