FOSSIL AND RECENT 



73 



is significant that the anterior border of the subtemporal fossa is ill-defined since this 

 invites comparison with Tarpon. The ventral border is clearly demarcated by a 

 prominent prootic-intercalar bridge which stands clear of the underlying exoccipital, 

 leaving a small foramen between the bridge and the lateral cranial wall. 



Beneath the subtemporal fossa the exoccipital contacts the basioccipital ventrally 

 and the prootic anteriorly. At the junction of these three bones there is a shallow 

 depression. The depressions of either side are only separated from one another by 

 a double layer of bone and consequently the saccular recesses must have lain above 

 these depressions, as in Tarpon. The exoccipital is pierced by two foramina. The 

 larger of these, the vagus foramen, is situated beneath the intercalar and directed 

 postero-ventrally. The smaller glossopharyngeal foramen faces antero-ventrally 

 and is situated in front of and somewhat below the level of the vagus foramen. 



The intercalar overlies part of the exoccipital laterally and part of the exoccipital, 

 pterotic and epiotic posteriorly. Much of the intercalar is sutured to the exoccipital. 

 Anteriorly the intercalar is produced as a thin rod to meet a similar projection from 

 the prootic so forming the prootic-intercalar bridge. Posteriorly the intercalar 

 bears a small knob, bordered dorsally and ventrally by grooves, the ventral groove 

 being particularly prominent. The knob of the intercalar probably provided an 

 insertion point for a tendon from the post-temporal. The prootic forms much of the 

 lateral wall of the otic region and is pierced by three large foramina. Ventrally 

 there is a downwardly directed foramen for the orbital artery, dorsally a large 

 upwardly facing hyomandibular foramen, while beneath the prootic region of the 

 prootic-intercalar bridge is the posterior opening of the pars jugularis. This latter 



epo pr 



soc 



pto 



par 



f uv 



Fig. 37. Protarpon priscus (Woodward). Neurocranium in posterior view. 

 Based on B.M.N. H. P.356. 



