FOSSIL AND RECENT 



ors 



15 



I so. s.c 



pto 



asp 



Mot 



myp 



Fig. 4. Elops hawaiensis Regan. Neurocranium in orbital view. 



hyomandibular facet. The orbital face of the autosphenotic contacts the prootic, 

 pterosphenoid and frontal and is pierced by a foramen conveying the otic branch of 

 the facial to innervate the otic sensory canal. Internally the autosphenotic forms 

 the anterior wall of the post-temporal fossa. Ridewood (1904) stated that in Elops 

 saurus the anterior limit of the post-temporal fossa is formed by the pterosphenoid 

 (alisphenoid). This is not the case in E. hawaiensis. 



The lateral margins of the heart-shaped optic foramen are formed by the ptero- 

 sphenoid of either side which lies medial to both the prootic and autosphenotic. 

 The surface of the pterosphenoid is marked by a groove which curves upwards and 

 forwards from the opening to the pars jugularis. This groove contains the super- 

 ficial ophthalmic branches of V and VII. The trochlear nerve passes out of the cranial 

 cavity through the optic foramen. 



The orbitosphenoid lies anterior to the pterosphenoids. The anterior margin of the 

 orbitosphenoid is perforated by a large foramen through which pass the olfactory 

 tracts. Ventrally the orbitosphenoid is produced as a membranous interorbital 

 septum. Posteriorly the orbitosphenoid forms the dorsal margin of the optic fora- 

 men. The ventral margin of the optic foramen is formed by the ' wings ' of the 

 ' Y '-shaped basisphenoid which contact the prootic and pterosphenoid of either 

 side. The laterally flattened stem of the basisphenoid passes antero-ventrally to meet 

 the parasphenoid so dividing the entrance to the posterior myodome. The basi- 

 sphenoid stem ossifies late in ontogeny. 



The parasphenoid is long, extending from its contact with the vomer anteriorly 

 to the hind edge of the basioccipital. Beneath the orbit the parasphenoid is relatively 

 narrow but beneath the otic region it is broader as it forms the floor of the posterior 



