50 ELOPIFORM FISHES 



The posterior face of the basioccipital and the exoccipital provide a tripartite facet 

 for the first vertebral centrum, which is a functional part of the neurocranium. 

 The centrum bears autogenous parapophyses and a neural arch. 



The prootic is, as usual, of complex shape. The lateral face contributes to the 

 hyomandibular facet, the subtemporal fossa and the medial wall of the periotic 

 chamber. A stout ridge runs horizontally across the lateral face of the prootic 

 beneath the subtemporal fossa. The jugular canal opens near the posterior border 

 of the prootic, immediately beneath the horizontal ridge. The hyomandibular 

 foramen is large and points dorsally above the pars jugularis. In some (particularly 

 large) specimens an additional foramen (Text-fig. 23) is situated dorsal to the 

 hyomandibular foramen (Greenwood 1970a : pi. 3, fig. 1). The significance of this 

 foramen is not clear ; it may provide a separate opening for the efferent hyoidean 

 artery. Another foramen of inconsistent occurrence may be seen immediately 

 posterior to the hyomandibular foramen. Greenwood (1970a) identifies this as ' the 

 foramen for the head vein ' but this is unlikely since in the specimen figured (Green- 

 wood 1970a : pi. 3, fig. 1) there is a foramen for the head vein in the usual position 

 and also the foramen in question has no connection, direct or indirect, with the pars 

 jugularis but opens into the post-temporal fossa. Dissection of a specimen showing 

 a foramen in a similar position failed to reveal any function. A palatine branch of 

 the trigeminal nerve leaves the prootic by a slit-like foramen beneath the level of 

 the pars jugularis. The orbital artery pierces the prootic near its suture with the 

 parasphenoid. 



The medial wall of the pars jugularis is pierced by two large foramina. The pos- 

 terior and more ventral of these is the facial foramen while the anterior is the tri- 

 geminal foramen (the profundus ciliaris also passes through this foramen). The 

 anterior face of the prootic contacts the autosphenotic and pterosphenoid dorsally 

 and the parasphenoid and basisphenoid ventrally. The anterior face slopes postero- 

 ventrally from its dorsal contact with the pterosphenoid. Ventrally the prootic 

 turns horizontally meeting its partner in the mid-line to form the prootic bridge. 

 The abducens nerve pierces the bridge. 



The pterosphenoid is inclined almost horizontally. The trochlearis leaves the 

 endocranial cavity through a small foramen in the prootic. It passes into the 

 pterosphenoid to run forward within the bone, leaving the pterosphenoid at its 

 anterior limit. The anterior margin of the orbitosphenoid is notched by the exit 

 of the olfactory tract. The orbitosphenoid forms the anterior wall of the post- 

 temporal fossae. 



The median basisphenoid has a stout pedicel which in older specimens becomes 

 firmly attached to the parasphenoid. From the posterior border two postero- 

 laterally inclined prongs enter the posterior myodome cavity. The median basi- 

 sphenoid pedicel bifurcates dorsally to form two short wings which contact with the 

 prootics. 



The post-temporal fossae are enormous. The posterior opening of each fossa 

 is deeper than wide (cf. Megalops). The fossae extend right forward to the 

 anterior end of the orbitosphenoid and meet in the mid-line above the endocranial 

 cavity, from which they are separated by cartilage. The increased depth of the 



