354 



Proceedings of the Royal Physical Society. 



extremity of the hyomandibular towards the articulation of 

 the mandible ; this I do not insist npon, as it is not corro- 

 borated by any other specimen, though the existence of a 

 cartilaginous one may be safely assumed, considering the large 

 space between the lower extremity of the hyomandibular and 

 the articulation of the lower jaw. 



Fig. 3.— Head of Chonclrostcus (British Museum, P. 2048), seen obliquely 

 from below, showing the position of the mouth and the symphyses of both 

 maxillse and mandibles. The suboperculum and branchiostegal rays are 

 somewhat injured. 



The ceratohyal {cJi., Figs. 2, 3, and 5) is also very easily 

 recognisable, and requires no special description. 



Opercular apparatus. — The opercular flap is principally 

 supported by a large, broad, somewhat irregularly rhombic 



