Midway along its length it angled downward and was per- 

 forated by the hyomandibular foramen. Just below the 

 angle, along the posterior outer margin, was the articular 

 area for the opercle. There was no opercular process. Distal 

 to the hyomandibula and lying between the outer and inner 

 condyles of the quadrate area was a rectangular symplectic, 

 which took part in the articulation of the lower jaw. 



Attached to the medial aspect of the symplectic, at its syn- 

 chondrosis with the hyomandibular, was the ceratohyal 

 posterior. 



The ceratohyal segment of the hyoid arch was long, slim, 

 and curved and it subdivided about midway into anterior 

 and posterior ossifications. The anterior end of the cerato- 

 hyal segment articulated with a medially directed hypohyal, 



-ethmosphenoid diviston- 



-otrcoccipital division- 



nasal capsule 



superficial ophthalmic VII 



t V, 



prespiracular process 



otic branches of VII 



suspensorial crest carotid canal 



pituitary vein foramen 

 bosipterygoid process 



palatine branch VII 



fossa Bridget 

 cartilage 



suprabranchial I articulation 



occipitospinal nerve 

 X foramina 



IX 

 lateral commissure canal 



articulations of pharyngobranchials I, I 

 estibular fontonelle 



nasal capsule 



otic shelf. 



fossa Bridget 



supraotic fenestra 



.otic branches of VII 



croniol cavity (seen through 

 basicranial fontonelle 

 hyomandibula articulation areas 

 oteral commissure canal 



vestibular fontonelle. 

 endolymphatic foramen 

 occipital ortery canal 



B 



suspensorial crest 



prespiracular process 

 hypophyseal fontonelle 

 bosipterygoid process 



notochord socket 



palatine branch VII 



aortic groove - 



notochord canal 



articulation 



of pharyngobronchiol I 



Figure 4-30. Endocranium of Eusfhenopferon. A, lateral view; B, dorsal view; C, ventral view. (After 

 Jorvik, 1954) 



CHOANATE FISHES 



95 



