i3« 



ELOPIFORM FISHES 



SOC 



Ot.S.C 



asp 



exo 



fm np 



5mm 



Fig. 63. Pterothrissus gissu Hilgendorf. Neurocranium in posterior view. 



limited extent ; it is pierced laterally by the large anterior opening of the pars 

 jugularis and medially by the oculomotor foramen. The relationships of the rami 

 of V and VII to the pars ganglionaris and pars jugularis are similar to those described 

 for Osmeroides lewesiensis (p. 99). The prootic bridge is narrow and separated 

 from the basioccipital by cartilage. The anterior margin of the bridge is indented 

 where it forms the posterior half of the hypophysial foramen. Posteriorly the 

 abducens nerve pierces the prootic bridge. 



The autosphenotic contacts the pterosphenoid medially and the prootic ventrally. 

 Laterally the autosphenotic is produced as a short ' spine '. Postero-laterally the 

 autosphenotic contributes to the dilatator fossa and the extreme anterior end of the 

 hyomandibular facet. Much of the autosphenotic is overlain by the frontal. The 

 otic branch of VII, which in most teleosts pierces the centre of the orbital face of the 

 autosphenotic, here pierces the suture between the autosphenotic and pterosphenoid. 



The pterosphenoid lies posterior to the orbitosphenoid, antero-medial to the 

 autosphenotic and medial to the prootic. Part of the border of the optic foramen 

 is formed by the pterosphenoid. The orbitosphenoid is quite large and in the largest 

 specimen examined (B.M.N.H. 1903. 5. 14. 142) is produced anteriorly as a single 

 median plate which bifurcates distally and is connected to the lateral ethmoids by 

 short ligaments. The surface of the orbitosphenoid is marked by a prominent groove 

 anterior to the level where the olfactory tracts leave the cranial cavity. 



