MUSCLES OF CERATODUS 



363 



upwards and slightly forwards, and then inwards below the 

 auditory capsule, but is not yet attached to this. The Epi- 

 hyal has separated in a 13-5 mm. embryo into three parts 

 (Text-figs. 35-7). The upper end — the primordium of the 

 oto-quadrate cartilage — is slightly chondrified and connected 

 by a narrow neck to the floor of the junction of the auditory 



Text-fig. 32. 



Cej-atohyat 



capsule with the parachordal. The middle portion — the Inter- 

 hyal — is an aggregate of cells between the outer end of the 

 oto-quadrate cartilage and the hyosuspensorial ligament. 

 It is separated by a little gap from the former, but abuts 

 against the latter. The lower end, consisting of cells in a 

 slightly fibrillated matrix, is the primordium of the hyosuspen- 

 sorial ligament. It does not yet extend forwards to the 

 Quadrate, nor until the 17-5 mm. stage. 



The outer end of the oto-quadrate cartilage joins the inner 

 surface of the otic process of the Quadrate in a 17-5 mm. 

 embryo. The Interhyal chondrifies in a 16-5 mm. embryo 

 and subsequently enlarges (Text-fig. 38). In a 17-5 mm. 



