FOSSIL AND RECENT 99 



adjacent to the vagus foramen may mark the point of exit of blood vessels and 

 minor branches of the glossopharyngeal nerve. The main glossopharyngeal trunk 

 left the cranial cavity through a forwardly directed foramen in the exoccipital, 

 antero-ventral to the vagus foramen. 



The intercalar forms a cap over the triradiate suture between the pterotic, epiotic 

 and exoccipital. The intercalar is small but is produced posteriorly as a prominent 

 knob for the attachment of the ventral limb of the post-temporal. 



The basioccipital bears a facet on its posterior face which together with a facet 

 on each exoccipital provides an attachment area for the first centrum ; this latter 

 structure is functionally part of the neurocranium. Ventrally the basioccipital is 

 grooved, but much of this groove is overlain by the posterior part of the para- 

 sphenoid. In transverse section the basioccipital is ' W -shaped, the wings of the 

 ' W ' enclosing the saccular recess of either side. The posterior region of the myodome 

 roof is formed by the basioccipital. Laterally the wall of the basioccipital, together 

 with adjacent regions of the exoccipital and prootic, is slightly inflated. This 

 inflation, developed to a greater degree in 0. levis, represents the lateral wall of the 

 otolith chamber. 



The prootic is the largest component of the lateral neurocranial wall. As seen in 

 lateral view the bone is synchondrally united with the pterotic and autosphenotic 

 dorsally and the exoccipital and basioccipital posteriorly, and syndesmotically 

 joined with the parasphenoid ventrally. The anterior region of the subtemporal 

 fossa and hyomandibular facet is formed by the prootic. A faint ridge upon the 

 prootic continues that upon the exoccipital to form a ventral border to the sub- 

 temporal fossa. Beneath this ridge and close to the posterior margin of the prootic 

 is a large jugular foramen which leads anteriorly to the pars jugularis. Posterior 

 to the jugular foramen the path taken by the head vein is seen as a faint groove 

 beneath the prootic-exoccipital ridge. A large hyomandibular foramen is situated 

 antero-dorsally to the jugular foramen. A short canal links this foramen with the 

 pars jugularis. The orbital artery entered the antero-ventral corner of the prootic, 

 close to its union with the parasphenoid ascending wing, and passed upwards 

 to pierce the floor of the pars jugularis. The external surface of the prootic is marked 

 by a narrow ridge of bone running from above the orbital artery foramen to the level 

 of the pars jugularis. This ridge, which represents a site of branchial muscle origin, 

 is characteristic of many albuloids. 



The anterior face of the prootic forms part of the posterior orbital wall. Dorsally 

 this face contacts the autosphenotic, medially the pterosphenoid and ventrally the 

 basisphenoid and parasphenoid. Two foramina pierce the anterior surface. The 

 larger and more lateral is the anterior opening of the pars jugularis. The smaller 

 foramen opens directly from the endocranial cavity and is the oculomotor foramen. 

 From the dorsal margin of the anterior opening of the pars jugularis there is a groove 

 running across the surface of the prootic and pterosphenoid. Within this groove 

 lay the superficial ophthalmic branches of V and VII. 



The medial wall of the pars jugularis is pierced by two foramina. The posterior 

 of these is the facial foramen, and through this passed the hyomandibular trunk. 

 The otic, superficial ophthalmic and buccal branches left the cranial cavity through 



