12 ELOPIFORM FISHES 



exoccipital before opening to the endocranial cavity immediately above the vagus 

 foramen. Ridewood (1904 : 39) noted that in Elops saurus the internal limit of 

 the deep subtemporal fossa is formed by the supraoccipital. The supraoccipital of 

 E. hawaiensis is not as extensive as that in the type-species and does not play any 

 part in the subtemporal fossa. 



The exoccipital exhibits both a lateral and posterior face. The latter face contacts 

 the epiotic and supraoccipital above, the basioccipital below, and with its fellow of 

 the opposite side surrounds the foramen magnum. In young individuals the margin 

 of the foramen magnum is often incomplete ventrally. In its dorsal extent the 

 lateral face of the exoccipital is turned sharply inwards to form the posterior wall of 

 the subtemporal fossa, while ventrally the exoccipital is inflated and together with 

 the prootic and basioccipital forms the outer wall of the saccular recess. The 

 saccular recess and the contained otolith are relatively larger in younger individuals. 

 Three, occasionally four, foramina pierce the lateral face of the exoccipital. Post- 

 eriorly there is a large vagus foramen directed ventro-laterally and slightly 

 posteriorly. Anteriorly, close to the exoccipital-prootic suture, there is an antero- 

 ventrally directed glossopharyngeal foramen. The third constantly occurring 

 foramen is situated immediately in front of the vagal foramen and marks the point 

 at which a small branch of the glossopharyngeal nerve left the cranial cavity. This 

 accessory glossopharyngeal foramen is, in some specimens, preceded by another 

 very small foramen whose function could not be determined ; it may have carried 

 a small blood vessel. 



The intercalar ossifies very early in the development of the neurocranium. The 

 main body of the intercalar forms a cap over the triradiate union of exoccipital, 

 epiotic and pterotic. The ventral limb of the post-temporal is attached to this 

 main body. In lateral view the intercalar is produced ventrally and anteriorly. 

 The ventral extension partially surrounds the vagus foramen while the well-developed 

 anterior extension reaches forward to interdigitate with a posterior outgrowth of the 

 prootic. Together the prootic and intercalar form a bridge which stands clear of 

 the neurocranial wall, leaving a small foramen which may be seen in ventral view 

 (cf. Leptolepis dubia figured by Patterson 1967a : fig. 5). A small branch of the 

 glossopharyngeal nerve passes up through this foramen but it is doubtful if this is 

 the primary function of the foramen since it is inordinately large for the nerve which 

 passes through. 



The basioccipital is ' W '-shaped in cross section, the lateral wings of the ' W ' 

 enclosing the saccular recess of either side while the space beneath the central arms 

 represents the posterior myodome. The posterior portion of the basioccipital meets 

 the paired exoccipitals above in a triradiate suture, and this posterior face articulates 

 with a thin vertebral centrum. This first centrum is firmly united with the cranium, 

 so much so that in older individuals it is difficult to recognize as a discrete entity. 

 Ventrally this centrum bears parapophyses but no pleural ribs, while dorsally there 

 is an autogenous neural arch and spine. In small specimens the centrum is still 

 pierced by a notochordal foramen. The occipital condyle of lower teleosts is primi- 

 tively formed by the inclusion of a centrum into the neurocranium, but rarely is 

 there any associated neural arch. Thus Elops would appear to represent a primitive 



